I have several HP SpecAn with video output. No matter what I use for monitor and how I set it up, I could never get a stable picture that fills a whole page. Most of the times, images are shifted and falls off the edge. Also, it's a composite signal. If you are old enough to remember what monochrome APPLE II image looked like, that's what you can look forward to seeing.
You will also not be able to "tap into" internal CRT feed. It uses Sony module and depending on which one you get, sync speed is different.
If you are not going to do your own repair, you can think of those as throw away. (if you paid $1000 for one) If input amplifier goes or something serious with signal path, parts cost and labor will well exceed what you paid in the first place. As to tracking generator, it's quite useful. Only got-cha is even if you get 26.5GHz SA, tracking generator will only cover band 1, which I think ends 2.x GHz? In case of 8566 and 8568, it ends at 1.3 or 1.5GHz depending on which version you get.
I have my 8568 full stack on a heavy duty rolling cart. It works for me.