Welcome aboard! Try the search engine, you will end up with lots of posts to read about almost everything imaginable. Posting questions without the car specifics is tough on us, year make and model are essential.
Your sunroof problem is pretty universal with age. Sounds like your rails need a cleaning and proper application of MB sunroof rail grease(yes, use only this MB product in this case). Here is a link to a company that some things that might interest you.
http://www.**************.com/