http://www.skylinesaustralia.com/forums/topic/290880-rb25det-gearbox-crunching-into-4th-gear/page-3?hl=%2Brb25det+%2Bgearbox+%2Bcrunching#entry6033953
has some pictures. But yes you need a couple of different size pullers and a bearing press
Solid diff mounts increase the amount of NVH throughout the car, i would be checking all the bushes in the back end and your diff. Grab the diff yoke and move it up and down, 1 of the pinion bearings starting to fail will cause a bad vibration also