There are a number of challenges in drilling and reaming your own FSB pin holes in your barrel. One of the first is absolutely guaranteeing that your old FSB is perfectly aligned with the barrel's gas port, which is a challenge with any gas block, but harder with a standard FSB because of the part's size and bulk. Then you need the tooling - FSBs are usually installed with taper pins, so you need a reamer of the proper taper, and the pilot drill for that taper, and at least a good drill press to mount them in. Do you have a machinist's vise to put on the drill press' table? You'll need something very precise to keep the barrel and FSB in place and keep their alignment maintained while you do this.
The process isn't complicated: locate the FSB appropriately and keep it in place. Mount the barrel/FSB assembly in your drill press solidly and accurately. Drill the pilot hole perfectly centered on the FSB's first hole. Now change to the taper reamer and ream appropriately. Relocate for the second hole and repeat. It's not the kind of thing you can do without good tooling and lots of patience for a first try - I wouldn't try one myself, but if you're bound and determined to do it yourself, study up, get good tools to make it work properly, and then take your time when you do it. I'll be interested in your final product.