100$ might be a bit much, half the value is in the plugin. A 1A4 makes it worth more than a 1A1.
You're also buying the most complex 500 series scope. It's almost a certainty that the HV supply transformer will need to be rebuilt, unless you plan on using the scope 20 minutes at a time with an hour cooldown in between.
The CRT might be at the end of its life too, and no one rebuilds these anymore.
You will also need lots of skill in repairing and maintaining it. Tunnel diodes drift, making the triggers less and less responsive.
Have you ever worked on ceramic strips before? Stock up on 2-3% silver bearing solder (there might still be a roll of the stuff inside the unit, near the power supply regulators IIRC), and learn the correct soldering technique. There's also no refdeses here, except for the active parts. So you'll need to learn to navigate that as well. It's packed a lot denser than a guitar amp.
It's also full of voltages that will easily knock you on your butt, maybe even worse. But if you're playing with tube amps, you might not worry about this.
It also uses a mix of tubes and transistors, the tubes are easier to find than the transistors, finding modern replacements will be up to you.
Draws a lot of current, it'll heat you up as well.
Get the user manual. Everything is revealed.
I like my 547 and the many plugins I have for it.