Congratulations on this "score", Duos seem to be fairly hard to come by, especially working (!) complete systems with the Dock as well, and were one of the greatest realized concepts for business and the workplace ever, especially considering when they came out. I wanted one immediately and it would have served my needs perfectly, unfortunately neither the company I worked for nor I could afford them at the time.
The best thing you can do for any machine you inherit under any circumstances is to just start over. Run disk utilities/maintenance to seek and correct HD media problems, then reinstall an OS from scratch and do a (Norton's "Wipe Info" back in those days, among others) deep cleaning of all the unused disk space. Besides getting rid of unwanted cooties, you'll end up with as snappy
a Mac as possible. The old software is still out there and available if you don't have it. A couple days ago I just cracked the seal on the envelope of an After Dark 2.0 800K floppy disk contained in an unopened shrink-wrapped original box I picked up cheap on eBay a couple years ago, - works perfectly. Making a disk image and other duplication was the very next step. Sent it to another member here on the forum for his Color Classic.all the best!