Can YOU do it? Most likely yes, I didn't hide him too well. I have been wanting to do a where's Waldo style drawing for a long time now, and I'm so happy I just jumped right in! To be honest, I've always been intimidated to create a drawing with a lot of small details. What if I mess up? what about overlapping bits?
I found that If I just work from front to back, overlapping bits aren't much of an issue. I can do some variation (some alternating things ahead and behind eachother) as I go, but otherwise its a solid method.
The only thing I'd change is sketching the big building out first in pencil, drawing the characters atop it with ink, then inking the big building. This would give me the ability to put people atop it, and keep it proportional.