Welp, I just finished the Mater Cake and I'm reporting back like I said I would earlier today. It's not as beautiful as Bakerella's, but I'm happy with it.
I tried to follow the ingredient list and instructions as closely as I possibly could. I couldn't find the mini grasshopper cookies, so I just went with full size and cut them down with a paring knife. The cut edges looked kinda bad on the tires so I added splotchy chocolate frosting on the tires to look like mud and that helped. I'm still not very good at spreading the frosting smoothly, but I'm learning.
So...it's not beautiful, but Dad will get a kick out of it anyway. I'll give it a Level 1 on the GCT Fail Scale.