Hey Wardy, good video here. I wouldn't use a 4" angle grinder unless you were pretty experienced but other than that it's a great insight into what's involved. I feel more comfortable with a 6" inch orbital sander.

The other great resource for board repair is Eva the board lady, if you just google that there is heaps of good stuff on her site.
I always repair my own dings, satisfying and actually good fun! Because your ding is on the bottom and not on the rail it's going to be a little easier to repair. You really need to get those broken bits cut right out and fill the hole with a good stiff mix of epoxy and microbaloon style filler before you put the glass layers on. I'd actually probably do yours in two goes, clean out the hole mechanically, fill it with microbaloon mix and let that go off, sand it down and even sand into the surrounding glass around the hole to taper that gently into the hole. Then do the three layers of glass. Trouble is that to do your first repair you need to buy quite a bit of stuff. If you do it make sure you accurately mix the resin ratios. Best way I've found is to use digital kitchen scales, just put a layer of glad wrap draped over them before you start - I've learnt that drips of epoxy on the expensive digital kitchen scales doesn't go down all that well.....