2000 sts overheating

heater blows warm. thermostat and waterpump were changed last month

The surge tank is not cracked and the cap is a couple years old. I have a noise (water bubbles) coming from the console when I accelerate or rev up to 2000 rpm in park.

Temperature value is over 250 and to the redline.

The gurgling, bubbling noise can be heard just through the dashboard, like fluid rushing into another chamber.

Mechanic checked the puge line and said its fine. Thermostat I changed because it was never done before and the water pump went on the car so I had to replace. Temp gauge is at the 225-250 after 15 min of driving and will go up and down. Then will go to redline after an hour. Mostly redlines on the highway and have to pull off to let it cool down. But all this varies and redlines even city driving if I've been on highway for 30 min.

Can the head gasket be changed without pulling the motor out?

Who does head work on Cadillacs in Ohio other than the dealer?