One thing I'd be concerned about is that if you are getting into reloading and learning it, I agree with the conventional wisdom that doesn't think a progressive press is a good thing when you're just learning the processes. There are just too many things going on simultaneously every time the handle moves, to be confident enough that each round coming out is made correctly and has the right powder charge.
As far as is this press a good deal ...
Doing a little googling, Dillon's price for a brand new 550 is $419.
If this guy is asking $325 for one missing one or two parts, and it'll cost you about $100 and 6+ hours roundtrip (pretty much all day of one of your off days)... I'd just buy a brand new one with those $ figures. Doesn't strike me as enough $ savings to justify that big trip out there to look at it and buy it.
It'd be kind of iffy for me to grab that at $100 off even if it was in the same town, at least unless I could give it a good looking over in person.
If the $ involved are that crucial or your funds are limited, perhaps you could consider something less expensive?
Even if $ aren't a factor, I'm a big fan of learning with something like a Lee classic turret press. I learned on one of those, and the press is less than $100. It'll make up to 200 rounds an hour once you get used to operating it (after maybe a few months of using it). In a couple of seconds you can take out a plastic piece (or put it back into place) to turn off the autoindexing function, turning it into more or less a single stage.
Another popular way to get into reloading is to start out by buying a single stage press kit. If you want budget priced stuff Lee isn't bad, and if you want better quality stuff, you can get a single stage press like an RCBS Rockchucker or almost any other brand.
Just my opinion, but, I'd recommend a different deal to get into reloading. Some sort of single stage or maybe turret press is best for learning, or if you really want a progressive, maybe just pick up a brand new one. It doesn't seem to me that this guy is taking enough off of the Dillon to be worth the better part of a day of your time, if I have the prices about right. It looked to me like the other dies and accessories are on top of the $325 he wants for the basic press (minus the couple of parts he doesn't have).