NST Repair

Hi All,
I just recently purchased a few NSTs. Two of them have badly rusted nuts and
bolts but they worked just fine, that is until I messed one up. I got the
nuts off the HV terminals today, but had to work real hard to do it. I used
WD40, liquid wrench and elbow grease. After I got the new nuts on I noticed
that one terminal measures open. I took the nuts back off and when I wiggle
the bolt I intermittently get a connection. I tried to remove the bushing to
get to the internal connection . It moves slightly but won't come off.

Is there some kind of retaining ring installed internally, meaning that I
have to unpot the thing, or is it just the black tar goop holding it in? How
do I get this bushing off with out doing any more damage to the transformer?

I am sorry, I realize that this is one of those questions that belong on the
other Tesla list, but I can't seem to get plugged in to that list.