As far as shrinking the OS before installing on your phone, check out BB Boss OS Shrinker. I personally haven't used it, but a number of members have before installing OS6. Basically, you would install the OS you want on your computer (delete the vendor.xml file), run the shrinker program, and then install to your phone. Check out this how-to video:
YouTube - ‪Guide on how install LATEST OS6 on ANY BLACKBERRY! (Links in the description)‬‏