I probably should have been a little more specific with my question. Mainly I'd like to learn to do more of the routine maintenance. I clean out the lint, change needles frequently but I would like to do whatever is involved in a machine tune-up. I'm frustrated with the amount of time it takes in my area to have a machine serviced at the one reputable place near me, the next good place I know of is 50 or more miles away. I have a Janome DC3050 about 8 years old, has never needed anything but routine maintenance and I've used it on everything--lingerie, clothes, upholstery, quilting, FMQ even--it gets a lot of use! Also I have a 60 year old Singer, used infrequently and a Featherweight that would need a lot of work to make it useful.
Sewing Machines Institute is expensive if you go there and take live course but they do have dvd/mp3 course for under $300 and that's the one I was looking at.
I appreciate everyone's answers!