Enable developer mode in security>settings, that will get you terminal. If you want more hackability, there are custom kernels on this forum and there is always open mode. As far as repos, try warehouse, the N9 client for openrepos, and I am pretty sure coderus has one with some helpful stuff on it. I mostly install stuff from .deb files though.
I would also recommend fasterN9, its a big help, and if you dislike the standard meego styling like me there are a few themes in themes section of the forum

Welcome to N9land.