6 year old macbook pro

Your welcome, check out this link http://www.crucial.com/usa/en/compatible-upgrade-for/Apple/macbook-pro-%2813-inc h-and-15-inch%2C-mid-2012%29#ssdResults

Here you can use the scanner to verify what you are going to buy will fit in your machine. There is a 500GB SSD on there that is only 150$ which isn't bad. Please check out the link and do some research on your own as well before you attempt anything.

Based on the amount of ram you have you should be just fine in that regard, so just an upgrade to SSD will help your cause.

Full storage can definitely cause issues on your Mac. If you are able, update your machine to and SSD larger than your current HD, and increase your RAM if its 4GB or less. You would see significant improvements. Of course if these upgrades are going to be too pricy I would just upgrade. There is also the "I want a knew one" factor to pay attention too. 🙂

~Cheers, and good luck

Since you have a retina MacBook Pro, you cannot upgrade RAM as it is soldered. Other options exist for upgrading your SSD, such as:

OWC SSD Upgrade Kits For MacBook Pro Retina Display (2012 - 2013)

An off the shelf, SATA SSD will NOT work.

Apple still sells the 2015 models that are similar design wise to yours, both new and refurbished. They are a good in between in terms of cost and performance! An SSD + labour for your machine will likely run in the $300-500 mark.