I had your questions a few months ago, so I'll share what I learned and my experience, you're experience may vary. This story relates to a Facebook purchase, I have never visited the warehouse but would like to someday.
I was looking for a particular Pin, was having trouble obtaining, and a CoinOpWarehouse Facebook posting came up with the machine, claiming that it was in working condition. I had never purchased anything from him, and this would be my most expensive pin to date, but I saw that people claimed things on past threads and got the machines. I posted that I wanted the game and waited for some type of confirmation. After a while somebody else also claimed that they wanted it and then Lloyd commented that he would get the game. I was very confused and after a few PM's learned that just claiming the machine doesn't get you the machine, you need to quickly Paypal the money as well.
This made me a bit uncomfortable as I've never bought an unseen/untested machine before, but Lloyd said it worked, and other people had success, and the price was good, and Lloyd eventually agreed to sell me the machine and I sent payment.
I wanted to pickup the machine but learned it was in transit and hadn't made it back to the warehouse yet, and hadn't really been tested, they believed it to be working and purchased it as such. Made me more nervous but the price was really good and Lloyd said they would deliver it in a couple weeks since they would in the area and would save me a trip. Sounded good, and I asked if I could test the game to make sure it worked upon delivery, and Lloyd basically said it was as-is and did I still want the pin or a refund? I wanted the pin, but was now more nervous as I'm limited in repair experience, but the price was good, and free delivery, so I would wait.
After a few weeks I reached out to get status and there were delays and I would get it soon. After a couple more weeks I reached out again and there were delays and I would get it soon. My nervousness escalated, and during this time the same machine went for sale by a Pinsider in good condition for a little more, but I could get there and test it out before purchase. I reached out to Lloyd, couldn't get a definitive delivery date, and ended up cancelling the order and getting a refund with no issue.
Please note this is in no way to bash Lloyd or the Warehouse, I just couldn't handle the process. It was a bit of a learning experience for me and in the end I couldn't gut it out and chance what I was going to get in the end, as I was looking for a working machine with minimal work required.
I would say that if you're more willing to take a chance than I was and work on what you get, jump on something you see. Just know that you will need to pay quickly up front before seeing/touching your purchase.