Jumping in / retrofitting off the shelf copter

I have flown some quads and have been a tinkerer builder for awhile now. I have been slowly 3dprinting parts for a decent sized quad. However, before I go that far and have a big build with expensive parts and what not on a home build quad, I would like to start getting my feet wet with arducopter. So I am curious if anyone has taken some cheap off the shelf quads and basically ripped the guts out and use ardupilot with them. I have 2 quads at home that I would be willing to sacrifice to learning. I have a couple of radio receivers and a FlySky FS-TH9X-B to use.

Thanks for any help getting started!

Can you take a few pics of the insides of your quads you want to tinker with and give us some details of the components and brands.
The main thing will be if they have PWM driven ESC’s
does the radio receiver have individual PWM outputs or 1 PPM output?
Do your small quads have a seperate flight controller?

Ill get them opened up for surgery here soon and get some pics posted and get all my info on my receivers ect.