Can I install the lights after it has been built?

Rebekah Fifer Yes!  It's actually even how the instructions are written.  Frankly, it's almost harder to reverse-engineer to install as you build, as the light install is "top to bottom," but the build is obviously opposite.

I built my castle and the lighting kit came out a few months later (early adopter, as it were), and took maybe 2-3 days off and on to get it lit up (including the lazy susan mounting kit).