| It depends on how much you trust the GC or the factory to set the bias, but I'd say that you'd be safe to use them as is until you get a new set of tubes. I would hope that it's set reasonably well at the factory. To be safe, fire it up and make sure that none of the tubes are glowing cherry red or are off, and you'll all least not fry anything. Bias is somewhat a matter of opinion within certain parameters, some people like a really hot bias, some prefer a cold bias. I tend to be a little conservative. The bottom line is that if nothing is burning up and you like the tone, then the bias is good. Oh, and it shouldn't matter which tubes goes in which hole unless the tubes are seriously mismatched.
It might be worth learning how to do the bias yourself, but with the dangerous voltages involved, have someone qualified show you in person. Bias level is a personal thing, so it's good thing to have under your belt. | 
