Welcome aboard. There are some really smart and experienced people on here and I have no doubt they can answer your questions.
Until they show up, I will offer my less smart and less experienced 2 cents.
The first thing I do is check the fuses, are they the correct type and the correct rating? Beware if they are not, especially if they are a higher amperage.
If the fuses are correct then I plug the amp into a surge protector with no inputs and no speakers connected. If no fuses blow and no smoke or weird sounds after being powered on for 30 minutes, I power it down and hook up a pair of cheep speakers, I then power back up and listen to see if there is any weird speaker behavior. If all goes well then power down and hook up a cheep preamp and test the system.
This is the cross your fingers and hope for the best procedure. There is a much safer procedure using a Variac and a test bulb that hopefully someone will explain for you shortly.
