In my previous posts about wiring of the alternator I described 2 types. 1 with an RE60 regulator - this has an injector style plug connection on the reg! ( late model)
and an earlier model with an 005 regulator!
Either one will fit!

$50 sounds reasonable!
Just make sure you have warranty so you can take it to an Auto Electrician and get them to spin it up and check that it's Tip Top!
Other than that it sounds ok and you shouldn't have a drama!

One other thing is make sure it is the high amp alternator you are after!
It should say the amperage on the aluminium housing!
If you can't read it the easiest way to tell is by the stator! ( the stator is the round centre ring you can see inbetween the front and back housings! and the bigger this is the more amps the alternator is able to produce!)