Checking the PT is simple. If the PT is making ~6.3 VAC or so between each end of the heater winding, and ~650VAC or so between each end of the high tension winding, and 5VAC or so between each end of the rectifier winding, it'll be fine.
To check the OT, you need to unhook the OT primary and secondary windings completely from the rest of the circuit (with the amp off and unplugged), and hook each side of the secondary directly up to one side each of PT's 5VAC winding, and then (making sure the now-unconnected OT primary wires are not touching anything else) switch the amp back on and carefully measure the VAC across the OT primary. Make sure the OT secondary and the PT primary are not contacting/shorting to any part of the chassis or the amp's circuit when you do this. Its best to use insulated gator clips to hook the VAC meter up to the OT primary, and its best to use mains-rated insulated screw connectors to hook the Ot secondary to the PT 5V winding. The VAC between each end of the OT primary winding should be 160VAC or so (assuming it is an 8k:8R OT) with about 5VAC applied to the secondary winding. (Make sure your meter is on the 'hundreds of volts AC' setting to measure this)
The point of taking the board out is to check the wiring on the back of it throughly, and also to make sure the back of the board is properly insulated/separated from the chassis.