I always wonder were to post such info on the internet BUT this is as good as any.
Just bought

2001 ELANTRA GLS
134K
5 sp
Power locks

My fix for the front drivers door lock that is seized, not from cold.
The key did not turn the lock.

Pulled door apart from inside. Not too hard. keep track of small parts. Look from all. Door side is one piece but looks like two.
Pulled lock part out. 10mm nut on the left. Need to remove the bar that it moves to lock door.
May or may not need oil while doing process. I used a some.
Heated lock with torch on REAL low. Use tools to hold parts.
In my case nothing moved. Two ways to move, with key or with singer at end.
Now I did this over 10 or 15 mins. Heated, then stopped to see if things moved.
After some times things started to move.
Oiled with graphited lock fluid. Others please chime in with other good stuff to use.

Since the car is not on the road yet I will keep it out for a few days to see if it still works later.
I plan respray in a few weeks.

Good luck with yours.