It's easier on the 123s than on 116s. I have a friends that parts out a lot of cars, and he call pull a 123 dash in just over 10 minutes! I think it's worth it if the other dash is pristine. Just buy a good sunvisor and USE it when you park the car!
I'd also order new vacuum elements and replace all of that stuff while you have the dash out. Everything may be working fine now, but if they have never been replaced, they will give you trouble eventually...It's wise to do it while the dash is out if you can afford to do so.
Mike