ok how about a progress report: it isnt in great shape and i probably should have left it alone.

First of all, the whole assembly is way deep, like 3 feet lower than the basement floor. I believe it should have been installed so that the top of the cover and valve plate is flush with floor.

I stopped the constant trickle of groundwater (coming in through the bottom seam of the pit) with some hydraulic cement. Most of the time the top is submerged, which made it difficult to access and view before.

used wet dry vac to suck out water in the pit. Because the body of the gate valve is cast iron it was corroded.

loosened the two remaining brass bolts of which there should have been four noticed one bolt was missing, other hole completely invisible under all the gunk.

could not budge manual wheel handle to close shut of valve, so i tapped it with a hammer, and it seemed to break an air seal cause it started sucking or expelling air for about 15 minutes.
Now the wheel handle could turn, and so i turned it to closed position as per the semi annual maintenance directions say to.

Shortly after air stopped rushing, sewer water started to gurgle up, UNTIL it found level, and two holes previously drilled in the side of the pit.
Meanwhile, i am cussing like mad thinking i was going to flood my house.

At this point i cant really continue with the maintenance because the entire thing is submerged in black water. All i can do is try to start the bolts and tighten it back down- try to close it up. I realize that the cork gasket will not seal anymore and needs to be replaced, not to mention that one of the brass bolts was stripped and was just stuck in place by gunk.. SO now the valve is leaking, fills pit halfway with stinking sewer water.

Possible solution?
I can replace the corroded valve plate, four brass bolts, and the gasket , maybe set an extension adapter in so it will be higher than ground seepage water. pray it all works nice, even if its been a mess so far... i dunno.

Or i can call a professional with experience working on these old things.

After all i am not a plumber but someone who wanted to do much needed maintenance, this is my first experience with this sort of thing.
Leaving some things to professionals seems the wise course of action.

Am i crazy for attempting this " simple maintenance"?

Anyone out there give me advice, encouragement, tips, related experiences?