When you are ready, I would really encourage you to take the plunge! Mercury now sell a low-cost 3D printed back which is a lot lighter (and cheaper) than the DaYi. At the other end of the scale, the deluxe back would be the Linhof Techno Rollex 6x12... out of reach for me!
Medium format stereo is truly amazing, using an optical viewer and properly exposed and processed colour transparency film ... digital displays really do not compare (yet). When viewing, it's like you are standing exactly when're you took the photo, and you can look around the scene at your leisure, seeing things you did not see when you took the picture. It really is immersive and amazingly realistic.
The Sputnik camera is not a bad place to start, provided you "fix" it for its inherent light leaks and reflections. You need to save some cash for a decent viewer, they are typically $500-$1000. Arguably the viewer is more important than the camera ... it's certainly as important.
If you ever get around to this, feel free to DM me if you have any questions (not that I'm an expert ... but I've taken around 800 stereo pairs on 120 film in the past 5-6 years).