The enlarger looks like Omega C-700 to me. I have no idea what it is that is sitting under the enlarger and has few knobs. If it were me, I'd be comfortable paying $75 assuming everything works as advertised. In fact, if everything works, I'd probably jump on it.
Just to give you an idea, my enlarger has cost me $40. I paid $35 for the VC filters. I paid about $20 for the trays. I just bought a new timer for about $180, etc, etc, etc. You may not need everything in this package but for what you need, I think you are getting a good deal.
Oh, I don't think C-700 can do 6x7... but since I do not have that model, I'll defer to others. Typically, IF the enlarger is capable of that size (which I don't *think* it is), you'll need negative carrier, condenser, and lens.