Wow, $85 is crazy expensive. Even if they replaced the gaskets, poppets, posts, and lid it shouldn't be that expensive. Buy them online for less than $40, replace every gasket, and get some poppets just in case. The posts and lids are generally fine. If they're pressure tested there should be no problems. Don't buy a CO2 tank if you can put a deposit down on one at the local welding gas shop and swap it out as needed. Get a regulator online. Start with a picnic tap inside the fridge, you can always drill holes later. I recommend the door too, it's not a big deal to open and close with the beer lines and there's no danger of hitting any coolant lines.