Go to your system preferences for "Universal Access" and on the "Mouse and Trackpad" tab, check the box for "ignore trackpad when mouse is present". Screenshot here:
Unfortunately, thanks to the "unibody-ness" of this model, the keyboard and trackpad are built right into the upper case of the laptop. To replace it you have to pretty much completely dissasemble the entire machine. iFixit classifies this repair as "very difficult" though it can be done. You would need to buy the top case in order to do it, and paying someone to do it will be expensive because of the challenge of the task.
If disabling the trackpad brings your mousing back to normal then it sounds like the only other problem is the sticky keys on the keyboard. If you are careful, the tops of the keys can be taken off of the laptop without taking the whole thing apart. You need to be very careful with this as they are easy to break, but you may be able to take the bad ones off and do some (very careful) spot cleaning to keep them from sticking.