Chosen Solution
The trick is first creating a bootable USB thumb drive installer. That way you can swap the drives and then install a fresh copy of the OS onto the new SSD. Follow this guide: How to create a bootable macOS Sierra installer drive As for installing High Sierra I would hold off for now. Apple has some issues still with the new APFS file system running on SATA based SSD systems. The installer will install it even through you want the older GUID Journaled file system. You’ll want to create a new user account thats different than your current one. Getting your stuff off the old HD is also quite easy! You’ll need a SATA to USB adapter like this one: Startech 2.5" SATA to USB adapter. At the end of the OS install it will ask you if you need to migrate from another system this is when you can do it or wait until you get all of the OS updates and re-install fresh copies of your apps. Then locate the Migration Assistant app in your apps folder to do it then.
