[AnonHP]

Not GP, but as others have described here, you can clone your entire disk to an external one (using an application like SuperDuper! or Carbon Copy Cloner), upgrade the internal disk, and the restore from the external clone.

When it comes to hardware upgrades of the DIY kind, iFixit (https://www.ifixit.com/) is a great resource with detailed instructions, photos and even videos on how to do them for different devices. The site also sells tools and parts, but you don’t necessarily have to buy from there. For SSDs, OWC (Other World Computing, https://eshop.macsales.com/) has tested parts available for many older Macs.