It was indeed a pretty fancy flash, but digital has changed how TTL has to work. Digital has obsoleted all the old film TTL gear. But these can still work today, as always, if in Manual flash mode. It is just TTL that changed. Manual is not automatic flash, we have to control the flash power level ourselves, but this is pretty easy for one flash.
And the descriptions I see say this flash also has a PC sync connector, like the D200 has on its left front corner. That is one way that flashes are used off camera, with a PC sync cord. It can still work that way now, with the D200, even it if it is mounted only a inch or two off camera. It must be in Manual flash mode however.
The manual is at
http://www.cameramanuals.org/flashes_meters/sunpak_auto622_pro.pdf
Page 8 item 9 shows what it calls the PC connector. Can't really see it, but the picture looks more like a "household" connector at the the flash end, so I'm not sure about the cable. It may use a "household to PC" sync cable? Household connector is like on any table lamp, connector sometimes used at the flash end of sync cables, with PC on the camera end.