There are pitfalls
These have two critical unobtanium components in the high range. One is the input sampler microcircuit, and the other is the step recovery diode in the sampler driver.
These are the only high GHz components, the rest of the thing is all low freq. There is an HP PDF somewhere which describes it pretty well and the service manual is available too.
There is also an HP specific amp chip (0372 Limiter Amplifier) all through them, but you can usually source those from parts units - which are plentiful.
I have one in bits on my kitchen table, which works in the low range after I fixed a couple of the faulty amps. However it won't work in the high range.
The SRD seems to be dead, and I found a second unit which also has a dead SRD. The input microcircuit is also probably dead, although I haven't properly tested that as it took me a while to realise that the SRD wasn't working.
Sorry I can't remember the names of the modules off the top of my head. It's been sitting there for well over a month and I glare at it every morning and night
One of these days I'll put it all back together for use on the low range only. Too busy atm to try and come up with an alternative.
I got mine from eBay for $100 USD. It has the high stability ref option present and is supposed to have an input power limiter, but I don't think that was fitted for some reason.