1. I hear on the older Ultra it may not be worth your while - the way the head is potted makes it much more difficult, I gather. However, something from the thread titled 'Polished Infinity Ultra' regarding the NEW style may get you going in the right direction if you wanted to.
2. Go to the Sandwich Shoppe link on CPF, and look for 'Uncut Hi-Power 5mm LED'.
3. Quite noticeably. For beamshots, take a look at the thread 'Uncut MJLED rocks in Dorcy AAA (and others)'. I took some before and after beamshots with my Gerber and they looked almost exactly like the UK eLED 2AAA beamshots on that thread. A very useable gain.