Like the others have said - cut it upside down w/masking tape on the laminate side. I've never scribed w/a razor knife so I can't comment.
One thing to mention - I like to put a couple of 2x4's underside to hold the cutoff piece - set your saw blade to just cut the top & not thru the 2x4's...
My preferences:
Welder: Miller
Hand held 110v angle grinders, hand drills, protable bandsaw: Milwaukee
Cordless: Dewalt
Mechanics tools: Craftsman, Snapon, Proto
Compressor: Try & find an older oiled model w/a real 5HP 220V motor - 30 gal minimum.
Other shop tools: Keep your eyes open for estate...
Looks nice - I'll bet you'll enjoy it, nothing like 2400 sft for vehicles & storage. We lived in Warren back in 93/94 & remember it being the coldest & snowiest I've ever been thru (-44F @ the lowest). I much prefer the south!