A local pawn shop has an 870 Express/wood/3", 95-98%, for $130.00+tax. This 870 has the newer barrel-locking setup, with the plastic locking device that fits inside the mag-tube. Additionally, it has the old-style safety rather than the newer key/lock setup. Is this a good price for this 870?? Will my old-style, ball & detent barrel work on this gun? Conversely, will the new-style bbl. w/o the ball & detent work with old style mag tube cap on a different gun? If so, what locks the bbl. in place? Thanks in advance for your information.