Replaced HD with SDD, can’t load OSX dvd...

I’m suspecting you are hitting a bad HD SATA issue! Time to replace it!

Here’s more on the issues: Your Hard Drive Cable Is A Ticking Time Bomb. Make sure you apply a strip of electricians tape down on the upper case where the cable crosses to help protect it.

You want to use this part MacBook Pro 13" Unibody (Mid 2012) Hard Drive Cable and yes! This is the 2012 version of the cable. Here’s the guide to put it in MacBook Pro 13" Unibody (Mid 2012) Hard Drive Cable

Even still you need to be careful with the new cable as you can damage it in the process of installing it! Don’t fold the cable! Creasing it damages the foil wires. You’ll want to get an old BIC pen ink straw (empty). You’ll use it to help form the needed bends curling the cable around it. You don’t want the bend to be tighter than the radius of the straw.

Once you get the drive installed you’ll want to reformat the drive to make sure it doesn’t have any corruptions. But we do have another problem here! Your CD installer won’t work any more! If you've got an old macOS install image, it will probably stop working today While the article talks about the OS image file the CD is just another store of the same image file! The only different is its been setup to use the image as a boot volume.

What you really want to do here is to get the newer OS installer and setup a bootable USB thumb drive. I recommend sticking with Sierra on the older SATA based systems. Here’s the needed OS installer How to upgrade to macOS Sierra, jump down to Step4 make sure you click on the Blue URL link labeled Download macOS Sierra then follow this guide to setup the USB drive How to create a bootable macOS Sierra installer drive Once setup you’ll restart using the installer to boot your system and then follow the instructions.