Sony A300 not working

hello, i have a problem withy my sony a300, its dead !!
it has done just over 19,500 shots over 2.5 years
my questions are
firstly is it posible to fix and what sort of prices to fix would i be looking at. (how long do these entry level cameras usually last?)
the story below helps to describe the problem i was having.
while out with the camera, the mist rolled in off the sea and i carried on shooting abstract images, but then the camera, after a click, the screen turned white with a message saying "camera error", none of the controls would work so i had to switch camera off then back on again, then trying some more the camera worked once then failed again. switched lenses and the same happened, so gave up and went home.
at the house tried it a few more times and thought that perhaps the aperture control plate was sticking, any way the camera then decided it was not going to switch on again, tried freshly recharged battery and still no life.??? now i'm stuck!!
secondly, if i would need a new/secondhand sony dslr body, where would you suggest i look as i am very short on cash. (i may get to £400 as i was saving for the sigma 10-20mm wide angle lens.) i have looked at various sites like ebay but i worry about those and hope i can get advice on a trusted place to look.
thank you for your time on this.
Anthony.
it has done just over 19,500 shots over 2.5 years
my questions are
firstly is it posible to fix and what sort of prices to fix would i be looking at. (how long do these entry level cameras usually last?)
the story below helps to describe the problem i was having.
while out with the camera, the mist rolled in off the sea and i carried on shooting abstract images, but then the camera, after a click, the screen turned white with a message saying "camera error", none of the controls would work so i had to switch camera off then back on again, then trying some more the camera worked once then failed again. switched lenses and the same happened, so gave up and went home.
at the house tried it a few more times and thought that perhaps the aperture control plate was sticking, any way the camera then decided it was not going to switch on again, tried freshly recharged battery and still no life.??? now i'm stuck!!
secondly, if i would need a new/secondhand sony dslr body, where would you suggest i look as i am very short on cash. (i may get to £400 as i was saving for the sigma 10-20mm wide angle lens.) i have looked at various sites like ebay but i worry about those and hope i can get advice on a trusted place to look.
thank you for your time on this.
Anthony.

Anthony. First some advice (sorry not a Sony owner so it is a bit generic). To give the camera a chance try taking out all the batteries (often they have a watch type battery as well as a rechargeable one) and remove the lens and memory card. Then place the camera in a warm dry area with no lens and the compartments open. Leave it alone for a day then try it again. It is possible you have an excess of moisture in some of the electronics and this may help revive it.
If nothing else removing the batteries and then finding and performing a factory rest may well kick it back into life. On putting it back together try it with no lens and no memory card. If it responds try a factory reset and if its working try it with a memory card then with a lens. If it works with no card/lens but fails after you fit them then the body may in fact be fine.
Your description matches more what happens when you get moisture onto the electronics than mechanical failure. And I would worry that it is not economic to repair it.
If it is broken then I would contact a reputable Sony dealer or try one of their service centres. I know with Canon you can get a good idea of the cost prior to sending it off and you can ask for an assessment without having to go all the way to the full repair. Try looking in the Sony web site for a list of authorised repairers. Again reputable camera dealers are the best in my view and you can always look in the forums, but for second hand sadly there is less kit around than for Canon and Nikon.
In terms of dealers I have used then I like T4 for advice and service including organising repairs.
MPB are good but do not stock Sony,
Mifsuds have some Sony/Minolta stuff and an A700 is in stock in your price range.
If nothing else removing the batteries and then finding and performing a factory rest may well kick it back into life. On putting it back together try it with no lens and no memory card. If it responds try a factory reset and if its working try it with a memory card then with a lens. If it works with no card/lens but fails after you fit them then the body may in fact be fine.
Your description matches more what happens when you get moisture onto the electronics than mechanical failure. And I would worry that it is not economic to repair it.
If it is broken then I would contact a reputable Sony dealer or try one of their service centres. I know with Canon you can get a good idea of the cost prior to sending it off and you can ask for an assessment without having to go all the way to the full repair. Try looking in the Sony web site for a list of authorised repairers. Again reputable camera dealers are the best in my view and you can always look in the forums, but for second hand sadly there is less kit around than for Canon and Nikon.
In terms of dealers I have used then I like T4 for advice and service including organising repairs.
MPB are good but do not stock Sony,
Mifsuds have some Sony/Minolta stuff and an A700 is in stock in your price range.