I just realized your original post said to use Cephalexin instead of Amoxicillan...I had the leftover amoxicillan (date still good) but I'm assuming that's pointless with this type of infection then...
As far as the sterility: I lay out everything first- with the alcohol pads already opened so I can take them out without touching the wrapper. I wipe the Vial top and injection site with different pads. I change out the needle without touching anything, and I hold a pad to the injection site with slight pressure after poking, until I put a band-aid on it. You never know what's floating around in the air during the time the needle is exposed, though...
Thanks again..