Welcome!
The 430 hours is nothing for that engine. The whole deal is not bad, and that tractor is not underpowered unless one is trying to use implements that don't belong on it.
I agree totally with Bird about the rear finish mower. They are much easier to hook up, and it's not hard to cut around just about anything. The only real advantage to the MMM is if you have way too much close stuff to cut around. With the RFM you sometimes will have to back into and between things, but that's not all that hard.
Price-wise, you could get two good RFMs for the price of the MMM. and wouldn't have to spend the money for extra hydraulics.
You're right, you rarely see used subrame backhoes for sale.
The backhoe is easily removed, probably not more than a 10 minute job once you're accustomed to it.
Another thing about RFM vs MMM. The maintenance of a RFM is simpler and probably less costly as well.
Just make sure you guys get on that tractor and operate it for at least 30 minutes and operate every bit of the hydraulics and look for any problems. After about 30 minutes, most anything is going to show up. Try to use it to acutally DO something like drag a box blade etc. Use the backhoe and dig a little, checking out the swing and other operations for any glitches.
John
John