We are a Surly Bike Shop, we are super small so we don't keep the cross check in stock as we just don't have the room. We stock every size of the LHT and usually size someone and then order their bike, we try to avoid selling the bikes we have in stock - may sound weird to some but it works for us. We also will not ship a complete bike unless we have met the customer and personally fitted them to a bike.
Having said that, a true Surly shop (and sorry REI doesn't count) should be able to measure you and feel confident in ordering the right size cross check for you.
While I shop at REI for many things I have yet to meet someone at REI that knows enough about bikes to do a good job selling the correct bike.
The guy who tried to talk you out of steel is probably sitting on to much inventory and wanting to clear his floor, don't think I would be going back there.
Good luck in your search, stick to your guns and get the bike that works for you!
Sky King
____________________
Gilles Berthoud "Bernard"
Surly ECR "Eazi"
Empowering the Bicycle Traveler
biketouringnews.com