Tex,
This can be a big deal, and should take about 2 days to finish, weather permitting.
Make sure that they put on at least 3 coats of a polyurethane. A good polyurethane can be expensive.
Ask whoever what product they use. Ask for referrals.
I talked to a door guy once and uses some kind of cheap Walmart polyurethane. That obviously was priceless information.
A good refinisher should charge about $300 or less. One of the door experts in the community wanted to charge $2000 on an $1800 door, so be careful of ludicrous charges.
Bottom line, if the door gets a heavy duty beating in the summertime, you might want to think about a roll-up/down shade near the door.