It's an automatic, not too much you can do about it aside from replacement or manual transmission swap. I'm not entirely POSITIVE that the torque converter is *WORN* out, but that is definately the culprit in this "slipping" feeling we are experiencing.
Shoudln't be much of a big deal in terms of replacing it, just drop the old one out, and put the new one back in. I dont believe there are any special electronic parts that need to be replaced with it. Should be a simple replacement, could take a while in labor since the related parts are quite heavy. I'm no mechanic, so get a quote. :P