My daughter had this surgery her senior year of high school. (2002–so a long time ago.) She was in a full length leg brace for 8 weeks, but was allowed to remove the brace to bathe and eventually to sleep.
She was able to use her crutches to get into the bathroom, then could balance and/or hop on one foot to get herself onto the toilet within the first week. She could also transfer herself from sitting on the closed toilet into a stall shower directly across from the toilet by the end of the first week. In the shower she sat on a shower stool/shower chair and was able to bathe herself. She was then able to push herself to standing on one foot, grab a crutch and get herself out of the shower so she could get dressed.
Stairs will be problematic for the first couple of weeks or until he becomes very proficient with his crutches. Staying with his friend w/ an elevator during his recovery will make his life much easier.
The first 2-3 days after surgery will be the most painful and most difficult. D slept in a recliner the first couple of nights because it was more comfortable for her and she could elevate her leg.
IIRC, she was back in school about 10 days post surgery.