I'm calling a time out!

You might wish to reassess your ability to build your own....between your skill level and now seeing that you live in a condo/apartment. I own a house and do all my plywood cutting outside...will you be able to do that. If you do decide to go forward, you mentioned you had a circular saw. I would make the cuts yourself using a speed square on dimensional lumber and a straight edge that clamped to the plywood to cut the plywood.
The speed square can be had at Harbor Freight for a couple bucks:
I'm looking up the straight edge to see if they carry it or if you'll have to get that at home depot....so I'll edit this in a couple minutes.
Saw horses would also make the job a bit easier.