great! Thanks. I've got 5 shells left of the good stuff and it's the last week of deer season
OK, sorry if I wasn't making my original question clear, but here's the answer for the next person:
The spring curves like a 'u' when looking at the rear sight from the side. I just had to drift the whole rear sight assembly off to get the spring out after putting it in upside down.
Man, these guns are tough!
Rear sight is back in now :-)