I'm not sure exactly what you are asking for, and what you want light to be shed on, but hopefully the following may help.
Regarding using 3D solid modelling to check fit, you would have to model both parts in the software then you create an assembly (at least that how mine works - Alibre Design, similar to Solidworks). The software has a feature that checks for interferences, i.e. where one part is actually passing "into" the other part. Once "assembled" you can also visually see gaps, etc, that you may not have expected. You can also hide parts, so for example if one part is actually a sub-assembly of single solid parts, you can hide the individual ones to expose others that were hidden. You can also create section views where a plane "slices" through the middle of a part, sub-assembly, etc so that you can see how things fit on the inside.
As for how to do all that in Solid Edge you really need detailed video tutorials. One source that "hires" videos is this one:
http://www.solidmastermind.com/cdn/cate ... tutorials/
When I was playing with SolidEdge2D there was hardly any decent training videos and the above was the only one I could find. I even wrote to Siemens telling them that they offer their 2D version for free, but there's not much info on how to use it. They agreed and said they need to address that but did zippo LOL. So I moved on to other stuff.
