No one answered your question about camera cleaning. I would suggest you find a good camera repair shop to do this for you. You want them to do a CLA - Clean, Lubricate and Adjust. They should be able to tell you if you have problems in the shutter or aperture mechanisms, and they should be able to determine if the meter/auto exposure system is up to snuff.

This should not be horrendously expensive. But unless you moonlight as a watchmaker, you probably don't want to tackle doing it yourself.