It IS possible, but not recommended... First off, dropped in water now dry, appears to work fine, is the typical start of a hellacious long repair needs... I would just trade this in for a new one in my professional advice.... however if you want to do this, Take off the back, Take off the front, Take off the main board on the back Take off the LCD Take off the LCD frame Take off the top cover Take off the front frame Disconnect the lens unit electronics, Now for the fun and VERY difficult part, I HIGHLY suggest just buying a lens unit as the lens has almost 8 ways it can go back together but only 1 is correct. Actually just buy a lens unit off ebay... usually only 30 or 40 bucks for this camera, IF you think the rest is okay... I would still trade in personally.
Yes, check out microtools , they have them on there.. however its possible you messed up the PCB as well, in that case its connected to the main pcb which is a Nikon only repair due to programming issues. Also if you attempt to replace, and it looks like poop, Nikon will kick it back for tamper damage and not repair at all. Good luck
I wont say yes for sure, but it does sound more to do with your power button assembly then anything... its possible its in a stuck position. its actually VERY common for iphone 4's to have a power button stuck issue... though normally you have to replace the plastic housing the holds in the assembly as well... or I normally do at least. Also clean out the housing and button area for any dirt or crud.
Sounds like a barrel tab broke, only way to fix is ordering a new lens unit, off e-bay. Usually after a lens unit, and a top cover needed for this camera... you will prolly save money just buying a new camera. unfortunate part of plastic point and shoots... If you want a really good Canon point and shoot series check out the G series... I believe they are on the G12 now, even the old G9 is a good one though.