One thing to watch out for is the locking lugs on the barrel. Make sure any used barrel has split lugs (two pieces, split lengthwise). All modern barrels have split lugs, but there are some old ones around with solid lugs that will not function with a G2.
With a .44 Rem Mag barrel, you want a good scope, like Leupold or Burris.
I have an Encore in .44 that is a lot of fun to shoot with my light handloads. I just bought a used Contender (stainless/synthetic) with a .44 barrel and a Weaver 4X scope and a three ring mount. I haven't shot it yet.
I also have a G2 with a .22 WMRF barrel that is my best shooter (after a trigger job).