For reference, I replaced the belt in my dryer last night. It took me 3 hours, I had to look up a few videos, I cut up my hand, and had a few “extra” screws at the end. But, the dryer works!
I’ve replaced the knobs and spout on my shower, and it wasn’t hard at all. You just pull them off, and pop on the new ones. If you are trying to change anything about the pipes behind that, I’d call someone.