You own a 2008 MacPro and let another person install an SSD. The whole point of the MacPro silver towers was that
they were USER upgradeable, no outside interference necessary. See where it got you.
Running with only 1.61GBs of free space is dangerous and could cause your mac to lock up and be completely unusable.
You need to free up space on that disk immediately. Once you have done that then you can investigate what is duplicated on your drives and delete items you no longer need.
To be on the safe side you really need to work out what you want your mac to do for you.
Use a bit of paper and write down what apps you want and need to open the files you have.
Any apps you don't need, delete them, or if they are apps like Photoshop etc that distribute
their files throughout your mac you will need to use their uninstallers.
Take the weekend to sort it out, the mac is your responsibility and not some other in an independent computer shop,
involving a third party always ends in a mess.