Do all the plug's & sample library's get copied over
"Copied over"..? Plugins are nothing to do with Logic, they live in your plugin folders. Logic doesn't touch those, and won't magically uninstall your plugins.
The main issue is with the Logic preset content. I'd take a full backup of your system app support/logic folder, because LP8 will delete some of the legacy content from LP7 (because it has reorganised some of this stuff) - so if you want to keep the old LP7 presets, space designer settings and impulses which may be referenced in old projects) backup that folder, and also the impulse responses so you can copy them back after the LP8 installer is done.
But it's wise to back this stuff up anyway.
Logic won't touch any settings you have in the user appsupport/logic folders (ie your own settings and presets).
As far as sample libraries - as long as you aren't storing any non-Logic stuff in Logic's system app support, nothing will change. You shouldn't be storing user settings and content in the system Logic folders anyway, leave that stuff purely for Logic content.
if in doubt, make sure you have a good backup of your stuff before proceeding, then you're covered in any eventuality.
and are there any issues with Sertao Pitch n Time as a Time Machine 'extension'.
No idea - check their support pages to make sure it still works in LP8.