Blacberry 8900 very slow and back button does not work
 

actually inherited a blackberry 8900 from my brother. By mistake i had some sugar water get into my keyboard and it stopped working. I sent it for cleaning and the service person told me that he cleant the thing and then upgraded my s/w now the phone has become immensely slow and the back button does not work and my camera button does not click .. he says that it is a internal keypad problem .. Also whenever i restart i am automatically transported to safe mode and during startup i have avoided that problem by keeping another button pressed but it is so slow that when the backlight is switched of it takes like almost 10 seconds to start again..could u suggest a solution i am in dire straits please help :(..
On a seperate problem even my trackball seems to stop workin at times and it does not give me the same response when i press it .. will i have to change that also.. its gonna cost me a bomb...