I also had Crohn's for roughly four years before my resection.
My hospital stay was either three or four days (can't remember exactly), but I had it done laprascopically which shortens the length of time needed in the hospital.
I was up and doing things (including exercise) in two weeks. Not everyone should do that though, increases the risk of scar tissue. The recommended amount of time to take off is roughly a month. She will have a post-op appt two weeks after to see how things are going.
It does take a bit of time for the bowel movements to slow down...and some of that may continue depending on what area is being resected. There are ways around this though.
In regards to testing hormones, I'm not sure why they would unless there was reason to suspect pregnancy...
B12 levels can be tested if your wife begins to feel tired or weak a few months after surgery.