If it were mine, I would use drip edge, capping, transition flashing and cover the rake edge with preformed metal. Don't use roofing felt as an underlayment, use a high temp peal and stick smooth back underlayment. Where you order the panels will also have all the accessories you will need.
Roofing felt will degrade over time from exposure to the high temp of contact with the metal.
If he has 1x8 purlins running across his roof and he takes the old tin off to replace it wouldnt he just put the new tin back directly to the purlins. Should there be strips of the peal and stick covering the purlins? Or are you suggesting he cover the purlins with sheathing like he was going to shingle and then the peal and stick and then the tin?