For what matters just for driving and basic immersion - not too much really. The most difficult part would be trees IMO GT6 raised the bar for this little hillclimb track. You probably could make use of several nice 3D trees. Well not fully 3D, but 3D trunk with main branches, and then 2D sub branches. That could be difficult. But perhaps simple Y trees and bushes would be ok too.
A lot of stuff repeats there, large span tent pavillions, spectator stands, flags, fences, hay bales. Of course road itself, terrain, terrain part with the nicest lawn in the world, nice transitional object for transitional texture between road and lawn, that nice wall in the middle of the track, highly detailed physical mesh for road, wall objects which are not rendered, lots and lots of cardboard people, and of course THE house with an art structure. Good for basic. Then some skidmarks, a little bit of groove in sharper curves, maybe something extra, and you have early model.