I know it is confusing but let me ask a couple of basic questions:
Is your dish and receiver C-band only, or C and Ku band?
Did you install your C-band dish yourself, or let a professional installer do it for you?
With regard to the small dish, what service was that used with (if Dish Network or DirecTV, then that dish will be pretty useless UNLESS you want free audio signals, which are worth having. On the other hand, if it's an old PrimeStar dish, you're in luck as that is actually quite usable).
One thing you might want to familiarize yourself with is a DiSEqC switch. You will need one (and probably one or two splitters that pass DC through one port only). Some people may try to sell you a two-port DiSEqC - I'd suggest getting a four-port one because they aren't that much more expensive and someday you will wish you had an extra port or two. Try to get a good one with low insertion loss.
If your dish is currently C-band only then I'd ask a couple of additional things. First, what is the composition of the dish itself? Solid fiberglass, aluminum mesh, or what? If mesh type, how big are the actual holes in the mesh (can you stick a pencil through them or almost do so, or are they much smaller)?
If the dish is solid fiberglass or small-hole mesh, you may be able to make it receive Ku band by buying a dual-band feedhorn and a GOOD QUALITY Ku-band LNB (warning, there is one guy on eBay that sells CHEAP LNB's, they are pure junk, so be careful what you buy. I had one that crapped out whenever the temperature went below 45 degrees. Anyone in Hawaii, southern Florida, or Puerto Rico reading this that wants a cheap C-band LNB, let me know!).
It does not matter if your current receiver can receive Ku band, your FTA receiver would still be able to as long as you have a dual feedhorn and LNB's. But you still need your present receiver to actually move the dish from satellite to satellite and possibly to change LNB polarity (many FTA receivers can do that also, but in a dual analog/digital system you usually let the analog receiver deal with LNB polarity). I will note that Ku is initially much trickier to tune in - things like feedhorn distance from the dish and proper setting of the scaler rings on the feedhorn and such matter much more with Ku, but once you get it right your C-band reception should be crystal clear!
Once we know all this we can probably give better advice.
