I have mixed feelings on giving advice on matters such as this.
I install my own plugs, cut my dovetails etc.
I had "limited" knowledge of metal the first time and was petrified that I would do something a) wrong - bad and b) dangerous - really bad.
My first breech plug must have took somewhat over 20 hours - accomplished over three long evenings - that was a few years back. A couple nights ago I timed in an Allen Ohio patent breech in somewhat under 45 minutes (think I stopped for a smoke) and I do my fitting with nothing more than a file, machine square and a digital caliper (ok, I've had some practice in between, but no "formal" training).
I would consider cutting dovetails to be equally challenging - you make a mistake there - take too much metal and you could have a dangerous barrel.
I guess my point is, if you feel confident to do "either" operation, you should be capable of both.
Yes, you have to time the breech plug and if you jigger up along the way you may end doing a whole lot more filing to get things lined back up again - or maybe you put the makers marks on an lower oblique flat instead of the bottom (which I do often - I'm not overly concerned about getting it on the bottom flat - just out of sight)
No "contrary to all the scary stories you may hear", unless you do something catastrophically insane with the breech plug it is not going to blow out on you or cause fire/brimstone to fall from heaven.
If you do "not" get the face of the plug snug against the bottom of the tap hole, such that there is a tiny gap (less then 1/32"), it is not "immediately unsafe" but it does allow fouling to collect which can cause premature rust OR it could cause some gas cutting to shorten the breeches life significantly.
(and for those of you who trust the barrel makers, I would still pull the plug and check. I have personally seen two "breeched barrels" from a rather prolific company (who's name might rhyme with Soul Train) where there was a near 1/16" gap between the face of the plug and the bottom of the tapped hole - can't help but wonder how many barrels are out there like that and are shooting fine with the owner unaware - and that is scarier than breeching your own barrel).
I guess I'm saying - if you want to learn how to do it, find some good instructions, take your time (even if that means a few days of picking at it) and go for it.
It really is one of those things that once you have done it once, the second time around you are better and don't have to chase Tums with Pepto shooters worrying that you have jiggered something up :grin: .