Just a couple of notes.
A good established Viking dealer will be able to upgrade your D-1 machine to USB. Warning, it's pricey. My two machines still use the floppys and work just fine.
You will need to obtain some sort of software to write the designs to floppys in the VIP, VP3. or HUS machine language. There are several software versions available that will work. Most versions will translate to the language you need. Also when buying designs online (or freebies) you specify the machine language you need.
My advice: fine a good Viking dealer and discuss the subject with them. I realize they wil ltry to get you to trade up to the newest machine. You don't need to do that. My dealer realizes that I am not made of money. They already have several thousand dollars of my money for a (used) machine, 3D Pro software, and lots of design packs. I make a point of stopping in frequently to chat, show'n'tell my latest project, and buy at least a yard of fabric. They realize am retired and SS is not a fortune. But I am still a customer.
We all need to realize that face to face is sometimes necessary to comunicate. Several digitizers also do traveling workshops at local dealers. Anita Goodesign, John Deere, and Walter Floriani are all good, and friendly. $35.00 is reasonable for a 6-8 hr program. Go for it!