using existing leader for a civ mod

Question: If I were to make a civilization can I use an existing 3d leader head only, for my completely different civ mod or would there be major corruptions ?

No major corruptions unless you actually implement it astoundingly poorly.

Now, I don't know if you want to just use the entire leader from another civ or just the leader's 3D diplo screen, but either way it's pretty simple.
For example, if you wanted to just steal the entire Bismarck for your civ, all it takes is this:
Or if you just wanted Bismarck's leaderscene, that's one line of code if you've already got a new leader defined:

You Sir.. are a Legend, Thank you AgressiveWimp that's just perfect