With the amount of information that is available now there is no excuse for going to a dealer uninformed. Back when I was selling cars, even the salesmen did not know the invoice price of a vehicle. We were given a standard disount that we were allowed to take off of the MSRP for each model and that was it.
When I bought my Avalanche, the dealer posted the MSRP and Invoice price of all of his vehicles in stock on the internet. When we went in he laid a copy of his invoice on the table and we negotiated from that. Of course the kicker for me was 0% financing. I still can't believe that deal! The car business has changed. If you come in with no clue, many dealers will try to take advantage of you, but if they can tell you are an informed and reasonable buyer (that understands that they have to make some profit, but wants a good price), they will usually treat you with respect.
Do your homework and buying your Avalanche should be an enjoyable experience.
I tried to buy from my local dealer. They had one Avalanche in stock. I gave them a list of the equipment I wanted and 4 or 5 colors that I would accept. The salesman said "I might get a chance sometime next week to see if I can locate one for you". I thanked him and left. I checked the internet and found a dealer about 2-hours away with 22 Avalanches in stock, 4 of which were equipped exactly how I wanted. Sent an e-mail, got a call from the salesman, drove to the dealer, test drove the truck, took delivery and drove home. All in the same day. There is a world of difference in dealers. The good ones deserve our business.