Would like help on how to rate my old preamp

I have a Supratek Syrah preamp that I bought some years ago from a fellow Agoner. In terms of appearance, the preamp is about as good as the older Suprateks get (being handbuilt). There are no dings or rust that I can see. It sounds wonderful to me still after I rolled all of the tubes. Currently, the tubes in the preamp are worth more than the preamp itself cost me and I intend to sell them with the preamp as I have no need for them otherwise. However, the preamp has one issue. 3 times over the last 1 1/2 years of use I have had one channel drop out. A light tap on the side of the preamp brought the channel back and then there would be no problem typically for months.I presumed that it was likely that there is a poor wire connection? a faulty solder point or something equivalent. I am in my 70s now and slightly tremulous and never was DIY inclined.
My two great techs were long gone and so I asked the fanciest store in town about a recommendation of someone not too far away. I had used one of their recommended men once long ago to work on a Quicksilver amp and he did fine. I took the preamp into him but had an unsatisfactory experience. He had the preamp for over 7 weeks and then told me to pick it up, that he couldn't fix it without a circuit diagram. Not only that but in the time he had it he lost one of the feet and when I noted that at pickup, he accused me of not telling the truth saying that the foot was missing when he got it and then he randomly put another mismatched foot on. Obviously, I will not use this guy again.So, in reviewing the guidelines I don't quite know what to say. the preamp is not junk. It has been a lovely preamp for the money. The tubes, which include a pair of WE 417a's that I bought from Brent Jesse about a year before I bought my new Supratek Cortese. The preamp I believe could be repaired fairly easily (the jerk I dealt with also wouldn't contact Mick Maloney either, even when I said I would pay any communication cost) and the footer looks fairly generic to me and I bet a replacement could be got  easily. Mick has always been exceptionally easy to deal with aside from his living in western Australia. The preamp might even work for a long time without repair, I don't know. So how should I correctly assign a number under the condition category. I would just like to pass the equipment on to somebody who would like it and give me enough to cover shipping, fees and some value for the tubes that are in it (not that I would object to making a few bucks on it, but mainly I need to pass it on. Thanks for any help.