Randall, sorry, I was out of town today...for a really detailed/accurate site model use the sandbox tools (separate utilities download). Start with a contour drawing to create the site plane, use the drape tool (or extrude and intersect the drives, curbs, etc. yourself), then build your site features as you will. There are tutorial videos on all these steps...always an excellent place to start.
Or, simplify any portion of the site as you can/will. First extruding all the paving and such, I'd probably (but I'm not an LA) just slope the two sections of the site with the parking lots each toward the drive, then slope those two and the drive section of the site toward the street. Then I would do the same with major blocks of the remaining pieces of the site, positioning all vertically as they need be, and "stitch" the whole thing together.