Waterpump replaced, now overheating issues
 

Just replaced my waterpump. $1025.00. Now my coolant drains, and the temp guage is flashing, than steady red light, as the temp guage reads at high temperatures. I returned it back at the shop today. I cannot wait for this estimate or diagnosis. I am hoping it was the pump of course... "Porsche..There is no substitute!"
The picture was taken when the waterpump failed..... :(http://986forum.com/forums/uploads01/pump1342751672.jpg

probably wasn't flushed / bled correctly. air pocket in the system can cause overheating.
flashing light = "low coolant"
steady light = "overheating"

I think tonyc nailed it, plus it sounds like your shop didn't complete testing on your car before taking your money.

That's never happened to me before .... okay, maybe it has and my bill was over $4k for assorted work.

Any reputable shop would have fully tested it. I would also not expect to pay a darn dime more for them to fix it right.

There is a very specific process for bleeding the air out of the cooling system after draining the coolant. After I replaced my water pump, the coolant level went down ¾ gallon during the first time I drove it with the bleeder valve open. If your shop hasn't done this, then they didn't do it correctly unless they used a vacuum filler system.