But yes the flywheel will have groves in it from the last clutch disc. It is highly recommended to get it resurfaced or replace it.
Replacement will be less than $100 at any joe-smoe auto parts store.
You can have it turned at an O'riely's for $20 on average.
If the flywheel is turning when you try to remove the bolts holding it on.....
Put one of the bell housing bolts back into the back of the block half way////Use a flat bar or a larger flat head screw driver against the bolt and stick it into the teeth of the flywheel to hold it while you loosen the bolts holding the flywheel.
It wont spin then.