Try some fingerless cycling gloves for a quick upgrade to the comfort of your handlebar grips. I found Sheldon Brown's advice in this article actually helped me have a much more comfortable saddle without exchanging any parts. Of course, getting a new one is also absolutely fine.

As for the used market, I'd probably pick key words like commuter/road/touring bicycle. Bicycles generally age well, so you shouldn't have much problem with picking one that works just fine for your purposes. Going to the LBS and letting them do a routine check-up is always a good option, unless you want to do your own maintenance.