Easy way to find (x,y) on screen from (x,y,z) in game?

[Headhunter09]

So I want to create a window that appears in the center of a Part's transform and follows it around with camera movements, much like the existing Context menu system.

I looked at Camera.WorldToScreenPoint and such things, but I know KSP uses a number of coordinate systems, and I'm not that familiar with Unity's transform system.

1. How do I find the transform of a given part. Is it part.partTransform.position, part.partTransform.localPosition, part.transform.position, part.transform.localPosition, or what?

2. How do I convert that into screen space? Does the function above work, or do I have to do additional operations?