Valve complete pack?

Yes, but you won't get copies of the games you already own. The only exception to this rule applies to The Orange Box, where you get an extra copy of Half-Life 2 and Episode One if you previously bought them.

You only get extra copies of half life, what you already own you lose. And not just with this pack, basically with any steam pack like this.

by adding this pack, if you already own Half-Life 2, it automatically upgrades to Half-Life 3