I'm thinking about recording myself play lets say a rhythm part and a lead part on guitar, and want to combine them, but i'm worried there'll be that hint of timing that's off. are there any good programs that'd help me so i don't have to worry about this?
try using Powertab Editor, it is free and with it, you can assign a tempo and build a click track (much like a metronome) so you can play in the correct timing.
I was thinking of just listening to the track on headphones or something, but i'll give powertab a try, thanks.
Download Audacity. It is by far the most popular free program, and it is good.

It will do what you want. If you have any question about using, ask here and I'm happy to help. Or there is the Official AUdacity Help thread.
^ It's not a timing problem, it's a latency problem.

But you should always record to a click track when starting out, so it's a good call.