If your brother has the $5,000 to buy the rifle, it seems he should have the $50-$100 to have a gunsmith remove the brake without damaging the rifle.
However, if your insistent on doing it yourself you'll need the following:
Appropriately sized armorers wrench, large vise (mounted) with v-notched wood blocks to secure the barrel with, and most likely a torch to heat up the rock-set that's holding the brake in place. The wood blocks should be made of hardwood species, be about 2-3"x 4" x 6", and ideally made out of laminated stock to keep from splitting. The v-notch should be cut into the middle of the block and needs only be 1" wide and 1/2-3/4" deep. This "V" is the channel that the barrel will be held in place by, and then set in the vise to secure the barrel. From there the rest is as you would expect...
Again, by the time you've made the jig just to hold the barrel you could have had your local gunsmith do it. It's best if you disassemble the rifle and just bring the barrel as most GS charge by the hour. However, if you don't have an armorers wrench you'll be SOL.
Either way, I still think your best off just having it done by a competent gunsmith.