If the door frame is standard size there is a chance you only need door and not frame. If that is case just order door and pop it in and should be quick.

If need whole new frame hire a handiman.

I’d look at a smaller local independent window installation contractor. They likely have multiple options/brands of doors for you to consider.

An exterior door?

Zero chance I'd trust Wayfair (or similar) to properly handle an exterior penetration to the house and the associated flashing and trim work. If you're worried about the upfront cost now, watch out for what that could cost you in the long run.

Any advice for best options to affordable replace a door? Places like Anderson seem quite overpriced. Has anyone ordered from Wayfair or other online sites and paid for installation?