Sounds like a good deal. I purchased mine about 2 years ago, but it came complete with an omegatrol, lens carriers for everything from minox to 4x5, several saunders ($$$$$) easels, peak #1 focusing scope, 3 lenses mounted on the turret, absolutely everything I'd need to start printing from day 1.
Paid $250 plus shipping from L.A.
As for making large prints, yes 20x24 is not a problem considering you have the proper lens for the format you're printing, etc. With regards to losing quality, I've never lost any. In fact larger is easier to print on this enlarger, if anthing! There is a lever on the far right, that will allow for brighter light coverage once you start making particular sized prints. Flip that, and you're all set.
Good luck with your Omega.