What your describing reminds me of a stuck choke. Runs good cold, stutters and then dies when warmed up. Did you let it sit long enough to cool down and try restarting?
I know things have changed drastically with the computerized control systems, but it just reminded me of that.
Edit add on, Since you are there and the shop wont reopen till Tuesday, go to a local auto parts store and rent if you can or buy if you must a OBDII code reader to find out what the computer thinks the problem is. The units have come down in price to under $100 and can be used on any vehicle built since 1996.