Daniel! You are not being a pain in the behind. This is where you ask exactly the sort of question that you are asking.
I am going to assume HO scale. I just spent the better part of an hour looking through Walthers HO structures (all 4029 of them) and there doesn’t seem to be anything that captures the flavour of your dealership. However, I do see the dealership as a fairly easy scratchbuild, not that I would suggest attempting it as your first scratchbuilding project.
The building in the picture is not small by any means. However, you can scale it to fit your available space and still get the effect, or maybe leave off the back shop and just model the showroom and a bit of the lot.
Here is a suggested list of materials:
The dominant feature is the red tower with square cladding. That could be easily replicated using Evergreen Scale Models sidewalk sheets:
http://www.walthers.com/exec/productinfo/269-4517
or tile sheets
http://www.walthers.com/exec/productinfo/269-4061
Sorry, they don’t show a picture but the sheets have 3/8" x 3/8" squares with V grooves in between. They could be used for the tower as well as the rear side walls where the large door is shown.
The front side walls look like some sort of horizontal cladding, perhaps like this:
http://www.walthers.com/exec/productinfo/269-4061
The large windows can be made up using .060" square styrene stock (or there abouts), and clear styrene sheet:
http://www.walthers.com/exec/productinfo/269-9006
http://www.walthers.com/exec/productinfo/269-8606
The roof and rear walls can be made from plain .060" styrene