DIY - replace volume control

My tube amp has a volume control. Since I use an active preamp, I simply leave the volume control on wide open all the time. (There is no switch anywhere to take it in/out of the signal path.) Recently, the amp went in for repair for an unrelated issue. Somehow, the technician managed to screw up the volume control by 'fixing' something that didn't need fixing. Now, I'm trying to figure out how to make lemonade out of lemons.

Would the sound be improved if I removed the volume control? Can I simply remove the pot and directly connect the wires that meet at the back? Or do I need to do something else? Thanks!
If you know which of the 3 wires (per channel) goes where in your amp circuitry, you can "wire out" the pot.

Using a DVM, determine which of the three contacts on the pot is the "wiper". This will be the contact where the resistance varies as you rotate the knob. Then you need to determine which of the remaining two wires is ground, and the remaining contact is the voltage input. Short the voltage input to the wiper and you have removed the pot from the circuit. If you picked the wrong contact (ie you shorted the wiper to ground), you will easily know because there will be no sound.

The suggestion above will keep you at max gain but does leave the pot in loading the circuit. This may be desireable depending on the amplifier. If this pot is at the input stage it may be required to provide the proper input stage source resistance.

If you want to remove the pot completely, short the pot input wire to the wiper wire directly.

Could not say which gives the best sound. That is probably up to you to determine experimentally.
I had a preamp with a balance control (never used it) and was bypassed, it actually sounded better, transparency and detail improved. So any un-needed switch or pot that can be successfully removed from the signal path would be beneficial for sound quality. But you are in a unique situation where you can dispense with the preamp and use the amp's volume control plus have the ability to adjust the gain of the amp to match your particular preamp however that scenario does not offer any switching between components. If your technician is local I would insist on him making things right one way or the other.