Not long ago I found the same thing, 1100 with 26" fixed choke barrel. Nice gun at a good price.
Like you, I wanted to be able to use screw in chokes. I priced getting the work done and it was more than the cost of a brand new barrel with three chokes and wrench.
I picked up a 28" vent rib from Cabelas on sale for $219.
All factory, brand new and no wait for gunsmithing.
http://www.cabelas.com/product/Remin...h-All+Products