I see the website for this game lists two patches - 1.4 & 1.5. Are these included in the download already or should I go ahead and do it myself?

thanks in advance!

GOG's installer contains the latest version, so no need to patch the game. This is true for most games, with the possible exception of newer ones that take a bit longer to get the patches, and any unofficial patches, which GOG usually skips.
But for The Witcher, it is patched.

Witcher 2 had a patch to version 3.3 a while ago: http://en.thewitcher.com/patch3-3/

GOG's version for Download appears to be 3.0.1. Does it mean that the patch is not included and it takes GOG long time to update their download version, or their "3.0.1" includes this patch?

All of GOG's installers use their own version numbering. So I can guarantee that The Witcher 2 GOG has isn't version 3.0.1, and since it was updated quite a long time ago, I'd say it's 3.3

Edit: Seeing as the patch was published on 21st February, and I don't recall having any update notifications for the witcher, it is possible that you'll need to patch it. But this does fall under "Newer patches". I'd suggest checking on The Witcher's 2 forum, since this post is on the first Witcher's.

The witcher 1 DC from GoG installer is automatically patched to its final version. Which is not 1.5, but 1.4.something. Do not try to manually get it to 1.5. 1.5 was intended for the simple witcher game enhanced edition. GoG's once is director's cut actually. And they differ. Witcher 1=No need to update or tamper, if you got it from GoG.

The witcher 2 is another story. It is not up to date. Will require 4 updates after being istalled from GoG. You either let it download them from its launcher, or download and execute them manually from the above link. (official webpage, the witcher 2, support etc). It is still being updated, so when it will have its final renovation, then they might actually put its final version, here on GoG. Witcher 2=HAS to be updated, either automatically via its launcher, or with manual download and install of the 4 seperate patches.