guidance in resealing sheridan C

I'm looking for some pic's/directions that would aid in putting new seals in my mid-late 80's c series sheridan. I can find parts and a valve tool, but not the knowhow. I want to do the work myself, and would love to see power mods also. I enjoy working on guns, but have never tackled an air rifle. I bought this gun brand new when I was twelve or so and really want to get it back up and running.