Can I just rent a DIY kit and do this myself?

We’d steer you away from it. The hard part isn’t injecting foam, it’s controlling the lift. Foam expands fast and with real force. Too much in the wrong spot and you crack the slab or push it past level, and now you’ve turned a settled slab into a broken one. Reading the voids and metering the foam is what the job actually is. It’s not a forgiving thing to learn on your own driveway.