Yes, a full sized GPU will fit inside the case if you remove the block. I've built a Gtx 970 Strix (which is as enormous as the 980 Ti :-)) into my 440. It fills the case completely up, but it fits.
I think the block is held in place with Torx screws. I had to ask my neighbor for a set of Torx screwdrivers, so you should come better prepared than me.
I think the block is held in place with Torx screws. I had to ask my neighbor for a set of Torx screwdrivers, so you should come better prepared than me.