15K!
Hell I'll do it for 14K!
Just kidding

Step 1

Find a local shop or welder that does restoration work. I have found that on a nice weekend you can usually find lots of older nice cars at a convenience store. Stop the owner and ask him about his car and if he can recommend anybody to do your type of work. Many of the good and reasonable local shops do not advertise. I fabricated my own patches and my buddy welded them in. Took us about 2 hrs.

A) Labor to cut out old material and grind to clean metal (you can't weld to rust), my guess, 4-8 hrs
B) Labor to weld in new material, 4-8 hrs

If you weld to the backside or to close to painted surfaces you will burn the paint.

Good luck