That sounds like a good deal; I bought mine used, actually almost unused, for $1500 some years back. I thought that was a fair price!
Yes, you will need that front bracket; I'm surprised it doesn't come with it, as it's of no use for anything else that I'm aware of. The rear MMM attachments (a couple of steel arms that drop down) are part of the 3PH mechanism, but under the tractor, and should already be there. Ordinarily, those arms would be in the "locked up" position, so you might not see them; they attach at the two points on the rear of the MMM where those two spring-loaded pins are. In the second photo, you can see it on the right on the floor of the trailer.
The first time you mount it, follow the instructions in the MMM manual to set the arm heights properly (first photo).
That mower does a great job, BTW!
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