Ah! I'm so glad you found a good home for that nib! ^___^
Nibs generally just push in/pull out, but in practice it can get kind of complicated to get a good hold on them and everything. Speaking as a n00b here, mind. Like jar lid grippers might be worth a try. Grabbing a nib by the sides and wiggling it out is bad for it, but since you don't like the nib being removed anyway, it might not hurt (and it would get nibs out usually, er, before I knew better... ^_^; ). Sometimes the nib might not want to come unless you do pull the feed out along with it. If *all* else fails, knocking out the feed will render the nib accessible (drill a hole that the nib but not the section will fit into through a piece of 1.5" - 2" thick wood, put the nib into it, and use a hammer to lightly tap a rod of some kind (piece of dowel, backward sacrificial drill bit, etc) into the nipple).
Once it's out, the new nib (and the feed if it came out) should just push in.
After that, though, you'll want to check how the feed fits. It should rest against the underside of the nib so that it's not easy to slide a piece of paper in between them (I've heard the paper shouldn't go in, but I think it's going a bit far to say you shouldn't be able to get it in there). If there's a gap, heat some water (just short of boiling), dip *only* the nib and feed for about ten seconds, then press the feed against the nib for another ten seconds while it cools, to mold it to the nib. (I had to mess with this a few times to get it right. Works even better with a heat/embossing gun if you happen to have one.) Here's the site where I learned how to do that:
http://www.penmuseum.co.uk/master%202.htmGood luck!