I've installed my own cartridge style bottom brackets, but never a cup and cone style one. Would it be a good idea to get these installed by a mechanic, or is it easy to do on your own?

https://www.bikeforums.net/singlespeed-fixed-gear/208402-maintain-sexy-not-so-sexy-track-bb.html

It's easy and since they need some cleaning and regreasing once in a while you're better off learning it.

It's not hard once you learn how (and have a pin spanner handy.)

The directions onetwentyeight posted are very detailed and great... The only thing I would disagree with is to just use new loose ball bearings each time you repack it. They are arguably better (according to the late, great Sheldon Brown) than bearings in a retainer, they are cheap, and you know you will always have good bearings along with fresh grease when you maintain it. Some people may prefer the ease of using bearings in a retainer, though. YMMV.