plug and play, I don't think it is. I also do not know if the compass mirrors are auto dim. That said, if I remember correctly, the mirror with just auto dim has 3-5 wires in it, thinking 3. You may just have to figure out which wire goes to what and match them.
What year cars are we talking about here?
ok... found a picture of one on ebay: Here is the auction
It looks like it does have auto dim and that there are only 3 wires in the back. The plug is different from ours though I believe. The second picture also shows the compass bubble at the base of the mirror. Seems like a decent price for this.