freeze plug replacement difficulty? rear of driver's cyl. head GMC 305 V6

[Chuck78]

So while examining my clutch line/hose attachment with a mirror behind the engine on top of the bell, I discovered where a tiny antifreeze leak was coming from! My freeze plug on the rear of my driver's cylinder head has a hard scale built up on it and has corroded to the point where I have a real small leak. I tried to scrape the "gunk" off it it and realized that it was hard, crusty scale from corrosion.

I have 4-1/2" at most between the back of this head and the firewall. I'm lucky it wasn't hte pass. side, as it sits way closer to the firewall.

I'm looking for opinions on how hard this thing is going to be to remove. I've only removed freeze plugs from one bare block that was pulled, not sure how this will go with trying to do without pulling the head. Any ideas guys?

I was thinking right angle attachment on dremel, and try to drill a hole in it and pop it out. Not sure how well I could get a hammer and punch/chisel in there. It'd be a real short chisel or punch, and at an angle, if I were to try it.
I was planning to do my power brake upgrade and new separate clutch master on Monday, but that's just gonna get in the way of doing this freeze plug if I put all that stuff on the firewall.

Let me know what you guys think, as far as degree of difficulty and other ideas. I don't want to pull the head if this thing might be do-able other ways. Thanks!