Farmall AV PTO Question

I have a 1944 Farmall AV that I am in the process of restoring, the other day I was trying to clean off the rear end and came across a plug just under the PTO lever that takes a flathead screwdriver. I removed the plug and behind it appears to be something still in there but on the plug that I removed there are no signs of breakage and the piece still in there looks as though it is just floating in there.

I didn't do anything to it yet to try and remove it or put the plug back in place because I don't know what that is and don't want to screw anything up. I looked in my IT shop manual and also did a search on here but to no avail. Hoping someone can help me with this.

Also, I need to replace the rear end fluid (tranny, PTO) and was wondering the best way to drain it and what to replace it with and also if I should remove the rear axle housing pans and clean them off and if there is a gasket in those. Thank you in advance.

One more thing, anyone ever have the pleasure of removing the rear wheels from one of these high crops? Wondering if anyone has tips on how to get up that high to jack the thing up.

From the last pic do you think this tractor has been re-painted before, looks like there is a orangish color paint under some red, just curious.

Some pics:

It is the PTO shifter poppet. Look at the illustrations in the parts catalog.

The drain plug for the transmission is in the back on the right hand side of the housing. It has a square indentation in it that you use a drive to open like it were a socket. The fill plug is on top next to the shifter and it also has a square drive in it. The level plug is on the left hand side right underneath the brake rod. It has a square drive lug that you use a crescent wrench on. You add oil until it starts to come out of the level plug. The owners manual says it uses 5 quarts. I use SAE 90 gear oil. I also just recently took the final drive covers off and changed out the oil in them. They also use SAE 90 gear oil. Just make sure to wipe them out really good. When I removed them one cover had a gasket on it and the other one didn't. I would try to put some sort of gasket material back onto the covers. The fill plug for the final drives is just above the covers on the forward part of the axle. It has a recessed square drive and the owners manual says that it uses 1 1/2 quarts of oil.