While it's probably not required or necessary, I always recommend to do. This way you can fully inspect the gun, and make sure it's properly lubricated yourself.
I agree with this. This is something I used to do but got away from in the last few years. That bit me in the ash though with a PPQsc a bought a few months ago.I've seen a few brand new pistols that had defects that could be considered dangerous. Within the past few years, I've seen one pistol that had rust inside the chamber and rifling, and another hammer fired pistol that had the area of sear engagement so small that pushing hard on the hammer would allow it to drop. My gunsmith has told me about many more of these types of instances, with one including a pistol with a crooked barrel.
I'd always suggest cleaning the pistol first, more for inspection than anything else, but if you are taking the pistol apart anyway, why not clean and lube it as well.
The Walther video which abuwf linked to is a good one.
OP, a quick suggestion is that you smell Ballistol before buying it. Some people like it, some tolerate it while many others think it stinks horribly bad. Count me in that last group. It is almost gagging to me.
I currently have an even dozen gun lubricants and five gun greases on my workbench. Ballistol is the one I will never buy again solely because of the stink. When I made several valiant attempts to clean my guns with Ballistol my wife would not even come into the garage. I now use it ONLY on things that might need lubricant outside the house, garage or basement.
Just a suggestion.