IMHO. the key is to not act like a kid in a candy store. Just to preface, I am not saying you are/were acting like a kid.

I started off in November of 2003 - total n00b. I did an arse load of research on the 'Net before I made a purchase. This was before I found out about auctions.
I actually ended up called Betson (big time distributor) and asked if thay had any 19" JAMMA cabinets to get rid of (25" cabinets still fetch coin and can be sold to operators to use on a route). I spoke calmly and with authority. I told them that a monitor is not a requirement and it was better if it didn't have one anyway. They ended up selling me an empty Data East cabinet with coindoor and light fixture for $100. As I look back, it was a total hose for me - but that is beside the point. I feel, because I acted calmly and did not pester the crap out of the operator, this was the reason that the guy was very friendly to me and was giving me tons of freebees (buttons, joysticks). He even asked if I knew the JAMMA wiring standard. He even made me a photocopy of the wiring diagram before I left.
I did not innundate them with stupid questions. There have been 100's of people before you asking stupid questions - no need to continue the trend. The operator simply just doesn't want to have to deal with a n00b and all of his/her questions. That is what these forums are for. The operator just wants to pay his bills.
Hope this helps.
There is a FAQ floating around about how to deal with operators when wanting to buy something from them.
-Tom