STOP don't do anything yet!
Go directly to Apple either in person (Apple Store) or call their support line. They will replace the display for free!
Once you get your system back then and only then do you want to open it up to upgrade things.
But, even then you may want to think about it. The newer 'Thin Series' are harder to open and if you don't use the correct tools and technique you could kill your display. We've see quite a few people here who have damaged there displays so be very careful!
As to your options here: Yes you can put a larger HD in but you will need a special cable made by OWC. If you have a Fusion drive you'll need to first break the fusion drive set before you swap out the drives. There is no second SATA port for a second HD, you could put in a M.2 Blade SSD if you don't already have it, its buried on the back side of the logic board ( review the IFIXIT guide) and presently there is no 3rd party SSD offering for your system. While that maybe an option in the future its not now.