RE: cooling fan on 1999 4.3L vortec
Welcome to the forum.
You can go and borrow or rent the 2 piece removal tool or you can try using a large cresent wrench and a hammer.
I have sometimes had succes ( sometimes) leaving the belt on the pulley, putting a cresent wrench on the large nut and using a hammer with a quick hard hit on the handle of the wrench to loosen the nut.
Here's a pic for you.