Need help with some basics

Hi all,

So to sum this one up: I'm an Electrical Engineer learning to use SolidWorks for the first time. I've recently started work at a new company, and the task I'm currently on is to implement a new part number system. I have a hand-wavey idea of what I'm doing at best.

I'm struggling with two issues:

One- renaming PDFs is pain-free enough, but renaming part files and assemblies and/or relocating files makes SolidWorks complain. Can anyone recommend any tutorials or pointers for renaming part/assembly files with new part numbers without breaking top-level assemblies?

Two- I'm finding that creating parts from scratch is easy enough, but I'm having trouble with updating dimensions in existing parts. Supposing I want to change a length- I open the part, and click extrude1 (or whatever number the correct 2D sketch is from the feature manager, yes? Can I do this on a part I've saved from McMaster, and if yes how?

Thanks for any help, folks!

~Court

SolidworksGeneral