Originally Posted by
goldfinch
Your first error might be assuming that you definitely need to change these things. Why are you so sure that they need changing? You might need to step back on your trouble shooting. First of all, do you know how to adjust your cable tension and otherwise tune up your derailleurs? You should tune up your derailleurs before you start changing stuff. You might need to change out your chain. Do you know how to check for chain wear? If it is really worn, you might need to change out the cassette but unlikely the chain rings. Be sure to keep your chain clean and lubed. It should last more than 1000 miles.
Park Tool website has good instructions on adjusting your derailleurs. It will also show you how to check for chain wear.
I've done visual checks on the back of the chain slipping. A few of the teeth on both the cassette and the chain ring have worn considerably to the point of being sharp. Others are well on their way. I obviously need to change the way I use my gears but I can't do without the ones I am having trouble with.