Source Selector Fix-It Tips

The brother has an old Yamaha receiver that is having trouble with the source selector knob. When you move it, and sometimes when you don't, the channels fizzle in and out. You can usually fiddle with it long enough to dial them both in, but it's spotty and annoying as all get out. Now, I'm hoping that the thing is just dirty (it's about 12 years old) and that I'll be able to go in and clean it up. While I'm more than happy to wing it, I though to ask for a few pointers first. Should I be thinking about disassembling the thing and cleaning it, or would a good cleaning / lubrication do the trick? Would you want to put oil, grease or some other "wet" lubricant/cleaning agent on this sort of stuff, or is it best kept dry with graphite or the like? It may very well be busted and need more than cleaning, but I figure I should try this first. Any pointers would be much appreciated. Many thanks.