I don't bid on vehicles that I don't think are operational, it's not worth the hassle to me. If it was close by, I might feel different. I've previewed trucks but never ended up with one of those. All the trucks I have were bought based on the description, pictures and video.
If you can't preview, a video where you see it running and moving is good. Also look closely at the pictures for condition indications. Are the gauges working, amp meter showing in the green, ABS light off, air pressure up, etc. Keep in mind that sometimes pictures get mixed up so look closely to make sure it's the right truck.
I've bought 5 trucks from GL and only towed one home and I had planned to in that case. With that said, I bought the trucks for what I thought was a good price. Since the tow bills are huge with large trucks, I was ready to walk away if I found some major issue at pickup. Sometimes you have to be ready to cut your losses (pay the default fee), rather than throw good money after bad. You just have to figure out what is best for you.
Good luck.