Shown here in a 30 tonne press although I actually used a 10 tonne press at the time. It can then be used to press the new bearing back on just by turning it over. I was not able to just grind the old bearing off as the brake drum back plate which also acts as a bearing retainer would have been damaged.
Not sure how relevant this post is for Nissan trucks as I have yet to change a bearing on one but I imagine they are the same.
Incidentally for future reference, if you break out the ball cage and remove the balls then the outer race will come off allowing any back plate to be removed giving access to grind the inner race, does not need to be ground all the way, Rick