How can I have changes in my vimrc take effect without restarting VIM?
You can just source it, like this:
:so ~/.vimrc
Also, for convenience, it usually gets mapped to something quicker to type:
nmap <silent> <leader>sv :so $MYVIMRC<CR>
And then of course, it would be nice to open vimrc a little quicker:
nmap <silent> <leader>ev :e $MYVIMRC<CR>