If you have that many servers already, you should at least put up one for testing!
For SP3, you don't actually even have to stop the services (though you should for MR1).
There is documentation on BlackBerry's site that covers pre-reqs, I believe, but generally you can just download and install (note, MDS-IS needs to be uninstalled prior/during this process). You need to patch the BAS first, then the BES servers. Patching on the BAS will upgrade the database then patch BAS, after which you can patch the BES servers.