I've been playing KSP for just a handful of weeks now and I had a similar problem. One of my first "Loop the Mun and back" manned missions went horribly awry, and the vessel wound up in an eccentric orbit crossing Kerbin's around apoapsis. I believe in suffering my consequences for failure (Or at least the poor Kerbonauts suffering the consequences) so he's been orbiting out there for a while. I finally unlocked the nuclear engine and built a simple rescue vessel. It did take a fair bit of trial and error playing with maneuver nodes, but I was finally able to rendezvous with it, have the Kerbonaut EVA, collect his science, and board the rescue craft. Took another couple of "years" for the position to be right for a burn to be captured by Kerbin - Which took more Delta-V than I expected. But, a little Aerobraking and orbital adjustments by the RCS thrusters, and he finally made it home.
