Welcome! When you talk about isolating your scope are you thinking about a high voltage differential probe? I have the Micsig DP10007 and it's worked well for me when I need to measure a voltage difference at two points not at ground potential.
Welcome!
If you haven't already found them, owners & service manuals can be found by clicking the 'Manuals and Specsheets' link at the top of any page.
Welcome! The nice thing about all the gear you mentioned is that it's fully serviceable and restorable for a lifetime of enjoyment. I'm looking forward to following your progress.
Welcome!
In addition to the fine pre-amps that @Sk1Bum mentioned, also take a look at the Carver CT-7. It's a very nice performer and the remote control is a nice modern touch.