Back in the late sixties I used a Marshall 4x12 driven by a Leak TL50 Plus and a small single valve preamp I built to control the Leak.. it worked well but the cabinet WAS more than a little awkward to load in and out!
In this day and age, considering the power available from amplifiers, no one should still be using 1/4" phone plugs to connect between amplifier and cabinet. Never ever use an instrument cable for this duty!!
I've been using rack pre-amps since the early eighties when I built my first SS power amp. Since then I've enjoyed a few different units, some of my own build.
My current amp is a 2KW capable Class D stereo power amp. I built a three tube two channel pre-amp to drive it. It has served me well.
Thinking on this I feel that musicians not being able to buy tubes is a small price to pay to support the Ukrainian people in their time of desperate need.
As for the no fly zone that will escalate the situation with a man who has already shown a willingness to start to use nuclear weapons. God help us all if he goes that route. 😖
Personally I don't see those charges as too excessive. Folk do have the right to make a living plus profit. Not to mention the cost of some very specialized and expensive equipment.
Like as not the blown resistor is not the only problem the amp has. Also the circuit board will be easy to damage for the average tinkerer. It requires specialized tools which you won't own.
My advice would be to dispatch the amp to the authorized service provider and get them to repair it. You may be surprised at how cheap it may be.