I've decided I want to redo the floor in a checkered tile pattern and have a
few questions for you out there who have redone your floors.

I was going to do a completely new base floor with a piece of plywood, but
now I think I may just use the existing floor and put the tile on top. The
floor is completely out right now and ready to be tiled.
If I put tile on top of the existing floor, will that screw up how
everything lines up when the rear seat and cabinets are in? I was just
worried about clearance.
Sorry, I forgot to mention this is a Westy and the floor tiles are 1/8 inch
thick.

Also, when putting in the tiles, do I need to drill holes through the tile
for where the screws are supposed to go, or is the floor file without
screwing it down? I hate to ruin the tile job by drilling holes in it, but I
didn't know any other way.

If you have any tips, let me know. Thanks!