Everything should just unclamp. The shifters should fit ok if you have the down tube fittings which are curved to fit the frame - they may have bar end mounts which are flat.
Looks good. I'd guess a year or so either side of 1990.
Frame number will give it away. I have a 1990 with the 'Roberts' on top of the seatstay like that (653), also around the bb shell from about this time. Plenty of fades in the 1989 catalogue.