well generally before you step foot into a studio you should know your shit up and down. so i would say learn it the best you can.
if you cant accomplish this for whatever reason (time constraints ect.), then pipe a headphone mix of the guitarist playing live into your phones. either put him in a separate room and mic him, use the headphone out from his amp, or pull from a DI track. there are many ways to accomplish this.....
maybe playing to a click track wouldn't be such a bad idea either.