Nice find, David! That's exactly what I did.
I found an old 870 Trap gun with a full choke barrel for a good price. I ordered an 18½-inch improved cylinder barrel with sights from Cabelas, put on some sling swivels and replaced the original sights with some Tru-glo sights.
I didn't opt for the extended magazine because I've heard they don't seem to balance as well as the standard magazine, and I figured, that with the plug removed, five shots should do me just fine.
Again, congrats on the new acquisition.