Thermostat replacement - stuck open

[alecu]

Hello,
I have 160K and this winter I noticed the engine temp dropping while driving on the freeway at under 55 degrees. I had it scanned with DIS and there was also an error code for thermostat jammed open.

The previous did the cooling system at around 120K. As far as I can tell, all the other components seem to be fine, but the thermostat needs to be changed. I was hoping to wait and do the cooling system again around 200K.

The questions is:
Can you remove the thermostat without taking the pulley off the water pump. Is there enough clearance to get to the screws of the thermostat without removing that pulley?
Because if I have to take that pulley off, well, I might as well do the whole system again, but if not, I will do just the thermostat. I just need to know from someone who did this job to know which parts to order.

Also, is there a big danger of driving with the engine temp not in the "middle" while cold outside? The engine temp will go to the first white line and go back to the middle once I do city driving. Once the outside temp goes around 55 - 60, the engine temp will stay in the middle on the freeway also.