It's a fun project if you like getting your hands dirty. I also do most of the maintenance on my car that doesn't require pulling apart the motor. Also in my case I don't have to buy any tools because there are 5 bike co-ops in my area. They take appointments, have a suggested donation of $5, and have staff there to help.

Boro, you should check for that as well. Also there probably is a point to just taking up Walmart on the warrantee if you can; though I have a feeling its just what the bottom bracket on these bikes just do it. In my case it's getting some play so its time to replace it. If my bike was still under the LBS' warrantee I'd have them take a look at it.