Welcome!
7 weeks is very young, I'd be very, very careful - if it were me, I would not take a yorkie this young; it heightens the risk factor of heartbreak considerably.
But, if you are going to take him do/get the following:
Nutrical (petsmart)
Stuffed dog size of mom-dog (for comfort)
Pedialyte (in case of dehydration)
Vet's emerg. #
Feed him at least every 3-4 hours and make sure he's left to sleep quite a bit as well, they really need their sleep at this age and throughout puppyhood. He may not just eat dry kibble every 3-4, so you'll need to either get a high quality canned food, or home cook.
We're here to help, so just reach out if you need anything!
Congrats on your new pup, you will soon be in LURVE!
Ann