The color looks a bit off in the photos for "Galaxy Blue" which seemed to be one of the predominate colors back around '97, but the components seem to be consistent with a '97ish C'dale RT2000. Weight is just under 38lbs and cost new was probably around $2,200; the RT3000's were closer to $3k. I think his asking price is a bit too high; $1,000 - $1,100 would be more in line if it's really in pristine condition.
Components aren't all that bad, the worst being the rear Coda hub (a re-branded Hugi star ratchet) which tend to eventually come apart. However, if you are diligent about servicing / lubricating the Coda or Hugi hubs, they'll last many thousands of miles.
In general, it looks to be a great first tandem. Either give it a complete once-over to service all the lubricated parts (rear hub, headset, etc...) or have a trusted bike shop do it for you. Tires are probably 700x28mm, not 28" and that's about as small as you'll want to go on the stock Sun CR16 rims, originally spec'd for some pretty big and meaty tires, e.g., 35mm.