Chosen Solution
So, my wife’s 2012 13" macbook pro has been on the auto update schedule with Mac and is currently running High Sierra. She has 4 gig ram and and a 500 gig mechanical hard drive and the thing is struggling. I’ve ordered a 250 gig SSD from OWC and a ram upgrade, too (2x8 GB). I’ve done other similar upgrades and repairs to macbooks before so I’m not worried about the mechanical aspects. I’m hoping to get some advice on reloading the OS. Should I create a bootable disc? If so, what’s the best way? Should I take it to the genius bar and have them load High Sierra? Or should I go back an OS or two to Sierra or El Capitan? Thoughts?
In addition to what orgs said: I recommend putting the SSD in the machine so that you are certain out is formatted GUID. Do the RAM upgrade first and test that it works before proceeding to the HD upgrade. Closely examiner the HD/IR cable where it climbs over the last step and see if it has any indentations in it. I put pads on either side of this cable to prevent the bottom from coming into contact with it. A damaged one can cause your current symptoms.
High Sierra is stable enough this days sow no worries there. For the installation all you need except the screwdriver is a SATA to USB adapter for the new ssd. Start the MacBook, connect and initialize the ssd , download High Sierra from the AppStore and click install. Follow the instructions on the screen, when it asks for the destination drive pour to the ssd. Once the installation is completed it will ask if you want to migrate data to you new drive and here you select the option: from a start up disk if you want the data from the old one Or do not migrate data
