"All the Above".
Go back a few days and see a story just like yours. See the s**t storm it caused and how he messed the poor dudes' car up over a $20 deck install (a highly simple one at that-not anything like yours)!
$70 is a decent price for the install for that car. And as Luke mentioned, I HOPE you have the correct interface harness/ box. If you just have a cage and a Pioneer wire harness sitting in your parts collection, you are indeed short on parts. There is also a little custom fabrication to get a D3 to look right in that hole since there is no kit made for that car (that part is not a big deal for shops that have done them but if your "installer" is not a qualified fabricator, you will not be happy with the final finish.
I am not even going to go into what kinds of problems you will end up with going that route. I can tell you this, by now, you should be getting a few PM's from other long-time TR members telling you about our couple of shops on here that have taken care of their aftermaths from letting the wrong guy do the install.
Good luck with that one. As with Luke, we do not claim to be the cheapest nor the most expensive. We just claim to do the job perfectly everytime, as we have done for TR members and the like for YEARS. It has saved ALLOT of members ALLOT of grief and money...