Everything is done online now. V5 and tax.
Not if you need to change the taxaion class that can only be done at the Post office.
https://www.gov.uk/change-vehicle-tax-class/tax-due-to-run-out-or-changing-if-vehicle-is-exempt
I just had to go to change my new car’s tax over after i got my certificate from HMRC as it was on the scheme car.
Once it’s done you can renew it online.