I’ve done weatherstripping retrofits on ~5 doors, including a super drafty front door. It’s something you can do yourself if you are reasonably handy.
For weatherstripping the sides and top of a door, I’ve had great results from Q-Lon. I ordered it online as I couldn’t find it in local hardware stores.
For the door sweep, Home Depot sells a rubber reinforced door sweep, that I’ve been pleased with.