Well munin is not a web application, it just routinely generates a bunch of files and dumps them at the configured doc root, so there is no actual interaction at all between apache and munin. So if you want a dedicated http://munin/
url to work etc, then it's just a case of using tota;ly standard apache virtualhost configurations.
BTW, whilst the information munin tracks is good and detailed, I've found the application architecture to be just awful. sitting on a cron job and generating a dump of graph images... it's just horrible, and I'd suggest you looked around for less archaic products.