The warranty on the computer is the manufacturer's warranty, there is typically a sticker on the computer that indicates when the warranty will expire. If the sticker as worn off or is no longer eligible you can go the manufacturers site and put in the serial number to find out the warranty expiration date. Since the computer is a personally owned device, the computer is yours to do with as you wish upon graduation or leaving the University. You can check warranty status with one of the links below as it pertains to your computer.
Check Your Service and Support Coverage - Apple Support
warrantylookup - Lenovo Support US
Check your Microsoft warranty and create service orders
As for digital certificates and other things like email, UVA Box access, etc, that's all covered by ITS. Here is a link to their checklist information about when you leave the University. ITS will also be sending out information to all graduating students later this spring. https://in.virginia.edu/itchecklist-leave