Do I need appointment to leave Mac for service?

I suggest it won't be a bad idea to be proactive and make a reservation.

You can make a Genius Bar appointment for hardware/software service and support using this link:

Contact Apple for support and service - Apple Support

Get your Mac repaired and see how much will it cost:

Mac Repair & Service - Apple Support

Call Customer Support  (800) MY–APPLE (800–692–7753)

or on line  https://getsupport.apple.com/

or call  AppleCare Support at 1-800-APLCARE (800-275-2273)

Before making an appointment with Apple, review this article to see if it is a model they will still work on. There are limitations on how old a computer they can service.

Obtaining service for your Apple product after an expired warranty - Apple Support

That depends on who you're taking it to. If you plan to take it to an Apple Store, this time of year it's probably recommended that you make an appointment at the Genius Bar since they're likely to be swamped. If you're taking it to an authorized Apple service center, then you'll probably want to call them and ask.

Regards.