Looking at the front panel I would consider putting the volume pot where the power indicator lamp is. Then put the power indicator above the power switch. You might be able to get a Knob from Crate tell them one of yours is broken or buy it from them. I don't think shielded cable is necessary for the volume pot you can just twist the ground wire around the other two wires this should be sufficient.
I bought another amp from MF told them Best Buy had them for 85 with in store pick up so they matched the price and shipped for free I saved the sales tax.
You can see the pentode/triode switch in the last pictures I posted on the back panel and inside the cabinet in the picture that shows the reverb vector board.