Wow, you found a 576 for $190

Where was this auction?
Looks in great shape, not banged up and all switches intact and it's clean

We have an old 577 that we've been restoring, not nearly as well off as your 576, and had some issues that have been corrected and is working well now.
As you probably know, check the PS and all the electrolytic caps. We had a 10uF 450V that was leaking and replaced, strangely it measured ~10uF out of the circuit!! After some troubleshooting replaced a op-amp, also needed to carefully clean all the switches with CRC Electronics cleaner.
A trip to the local Ace Hardware for a few replacement knobs and such, then performed a subset of the maintenance manual cal procedure and the 577 is working nicely now!!
Later we also did a calibration of the 177 plug-in to improve the display accuracy & appearance. Quite impressive how well a CRT can display a voltage current relationship and how accurate Tek achieved results even in the corners.
The Tek folks of the day knew how to design analog instruments with CRTs better than anyone, they achieved very respectable precision and stable results with just modest components.
For the younger folks out there studying the design of these old Tek and HP relics can provide an insight into analog design and squeezing the highest levels of performance within component limits. Very similar to analog IC design where one is faced with a fixed set of devices with limited performance, and finding ways to expand/extrapolate/enable that into impressive results, Widlar of course the absolute master of such!!
Best,