The black goo meltdown is a fact of life with all the altec accordion style surrounds. Best thing is to flip the woofers 180 degrees every few years so it flows in opposite directions.
Not sure how badly you tore the surround but if not too bad I think you could use some preparation to repair this your self and get by for quite a while before a rebuild is necessary. Those surrounds are quite tuff and last a long time even with a tear or two and I doubt it would affect the sound at all unless it is a bad tear. I repaired one of my old ones with some black silicone used for installing windshields but it was just a hole where a screw driver went thru the surround.

Interesting how the driver is sunk into the rear panel and covered over with luan! Is it an 811B horn or the larger 511B?

Sorry I can't help with getting the grills off. Often wondered how this was done myself but I am sure someone here will help with that.

Nice speakers and basically they are the upgraded model of the 846 in a fancier cabinet. Many here swear they do best with tubes but I have had many and always was quite happy with good SS running them.

GPA can repair all the components so you are a few steps ahead of the Vintage game with Altecs.
Enjoy and welcome to the world of horny Altecs.

Gary