I guess I overreacted. I ended up cutting out the patch piece and was able to pull the depression back out of the door. I still have a very slight ripple that is less than 1/16" deep due to my inexperience with metalworking. Anyhow, I made a new patch piece and started to weld it in. This time I used the procedure described in this thread - one tack, then blow with air, another tack, blow with air, etc. So far I have a tack every 1/4" in and have had no warpage problems. I will be finishing it up this weekend by the same method as earlier - all tack welds until the seem is gone. I still need some bondo to cure the slight ripple, but I feel much better now that the depression is in a much more concentrated area and is less than a 1/16" rather than what I had before.
Thanks for your help,