Rad can stay put, as can rad fans if you have no issues, but often helpful to take rad fans out of the way for extra clearance, some pulleys are silly tight, some not.
Don't even think about lining up the marks at this point, as the marks will go way out of line after struggling with the pulley bolt.
Get the car on ramps, then put a good fitting socket on the pulley bolt, with a long breaker bar, or ratchet and tube, then as said put in gear(5th), then whack the breaker bar with a hammer to shock loose the pulley bolt.
Then get off pulley however it needs to be done, once nice and free refit partially on, line up marks tdc etc, and change belt as normal.
If the pulley is silly tight, use some valve grinding paste on the crank nose/pulley and lap it a bit, this removes the rust, and will after some 20-30 mins make it a better fit, you will of course need to drive out the woodruff key in order to be able to rotate the pulley on the crank nose, afterwards clean all paste, install key and put everything back.
tabetha