Check miyatacatalogs.com to see if it is indeed a 1000.

Clues to determine the model: the low rider pannier mounts on the fork, one eyelet on the rear dropouts, 2 water bottle mounts (one an top and one under the down tube), and lug work.

3 Things to worry about: that fort will likely need to be replaced. I had to do the same with mine. A unicrown fork would run me around $100 a new tange fork was about $250. Fortunately I lucked out an picked one up a my local bike kitchen. Also, maybe it's just unclear from the pictures, but what's going with the rear brake cable stop? It looks like it's missing. Finally, the fork may have broke from a crash, so inspect the frame for any warps.

Pros: $80 for just a miyata 1000 or 600 frame is not a bad deal. Miyatas were built really well and if you can scare up a fork, you're in great shape.