The trans wires wouldn't effect how it idles in park. You can remove the trans harness and it would still run.
If you had to remove the distributor make sure it is in correct location. There are 4 possible locations that you can put it. If you look at the bottom of it it will look like a Philips head screw.
Second make sure that you have the spark plug wires in correct order.
Third make sure that you connected the ground wires that you took off for the head job. even that little bugger by the fuel lines on the back of the engine.
If all is in order I would check and see if you have a vacuum leak. this is easy to do with a tool that you can rent from any auto store and connects in seconds. I can tell you how to do them if you need.
MAKE sure that you reconnected the wires to the MAF and IDLE air control on the air intake.
Are you showing any codes??
Did this SUV have a misfire before you did the head job?
Do you know you don't have a cracked block or warped heads?