If you are that close my advice (I have bought over 30 trucks from GL) is to preview the one(s) you are interested in and on the day of the auction stay glued to the computer.
Pick several trucks in order of choice and place the minimum bid on all of them as soon as the bidding starts.This will allow you to go to your bid history and see who (by bidder number) is bidding against you.
Set the max you are willing to bid on a truck and stick to it....don't get into a bidding war with somebody that has deeper pockets than you do. If you are outbid on your primary truck fall back to the next one on your list. Do not bid on more trucks than you can afford to buy.
I ended up with four trucks one time when I placed auto bids on a bunch. I was saved by the fact that I got them cheap and I had a credit card with a large limit on it.
GL takes a dim view of people that bid on items and can't or won't pay. They will lock your account and charge you a penalty if you default.
You can get some deals off GL but you dance to their tune and customer service (out in AZ) is not their forte. If you are nice to the folks at the sales sites they will be nice back (in my experience) and treat you right. Go in there with an attitude and they will bounce you off the lot and, if applicable, off the base.
Just my advice for what it's worth.