$100? When anything else you will see is $500 and up, why not?
I wouldn't use that to earn a living but for typical homeowner use I would just change the 90 wt gear oil (There's always water in there) and put it in service. See if it really needs those missing tines, or does sufficient work without them, before spending more money on it.
These things are near bulletproof. There is one part you need to check, and replace if needed: at the dumb end of the tine shaft, there's a ball bearing that will chew up the housing if it has rusted in place. It's simple to check, and cheap to replace with a standard sealed bearing.
You will likely conclude it is worth buying a set of tines and restoring it. Aside from that bearing and worn tines it should run for years with little attention.
You only need wheels if your tractor is underpowered, say under 15 hp, relative to the tiller. I needed them to use my tiller intended for 20 hp on my 15 hp (pto) tractor because it would dig too deep and bog down, didn't need the wheels for the 20 hp tractor.
That was about the last model that had wheels, they aren't needed when the tiller is matched to the tractor's hp.