mountain bike shifter replacement
I would like to replace the shifter and derailer on my Scott mountain bike. The bicycle is about 7 years old and the shifter has been a constant source of frustration. The entry level bicycle has Shimano Acera parts on it. I am hoping to do this job myself. The shifter appears to be sticking, so what happens is that when I hit the trigger to downshift it doesn't do anything, its almost like the trigger isn't attached to the mechanism. It stays in the gear "4" that it is currently in and if I flex the trigger up or down I can usually get it to catch.
The bicycle has an integrated shifter and brake lever. I can take photos and post if that would help.
I would also like to replace the derailer, a few years ago I crashed and broke the rear derailer cable tension adjustment. The mechnaic didn't have a replacement derailer handy so instead he just put it back in so that I could get back to riding.
What tools will I need (chain breaker) and additional parts / pieces to do this job?
If somebody could post links for the recommended parts. I am a recreational rider who maybe rides 400-500 miles a year but my spouse has recently found a renewed interest in riding so I would like to have a properly functioning bicycle.