Oh yeah, just reread your post and realized I forgot to reply to your question about the cold.

Unless the previous owner has record of it being done in the past two years you'd want to replace the glow plugs (minimal expense, relatively easy) and check the GP relay for problems. Given good plugs and good compression, you probably wouldn't have too much trouble starting it in the cold. -15F, don't know about, I live in FL. The coldest I've ever started in is maybe teens+, but it cranks right up.

Anything else you should know...
check any potential purchase extensively for rust if you live in Maine. Look for rust at jack hole points, wheel wells, under floorboards, firewall, sunroof area, trunk in and out. You might even consider making a pilgrimage to a SouthWestern state to find a nice, rust-free car.
Have a compression test done, you're looking for:
375-425+: Very Good engine, if this car costs around $3000, get it.
300-375: Good, not much to worry about.
225-300: eh, look around some more
225-0: walk away
See if when you turn the key to off the engine goes off right away. If it doesn't, this indicates leakage somewhere in the vacuum system. This can be a PITA to locate.