Katie,
You're all set to go! I'm glad that you will have home care, and that your wonderful hubby will be at home for a couple of days to assist you (and walk darling little Madison)!
Hopefully you'll be able to snooze a bit during the MRI today. Since nap time is precious, I've found that I fall asleep quite easily during MRIs and bone scans (with the headphones playing classical favorites during the MRIs). Of course, I also tend to doze off while having pedicures, as I'm so relaxed.
Maybe you can have a treat for yourself tomorrow - a favorite dinner that you and your hubby can enjoy or something.
You'll do fine with the general anesthesia, and I'm so impressed with your bravery. I've never had back problems, and can't imagine what you're going through now in addition to going through the healing process from your TKR. Hugs to you!