One of those machines that is worth some extra effort.. mind you, the game itself needs to sell at a reasonable price for this to be worthwhile.
Plastics aren't really an issue.. theres always someone who will scan them so you can make repros yourself,
Backglass can be bought here.. its pricey though..

http://www.pinball-shop.de/product_info.php?m=shop&p_id=1029&mcID=7&language=en

Apron?..Im sure a BALLY widebody apron could be sought.. the artwork isn't too much of an issue and could be replicated.
The Playfield is VERY restorable.
Machine would take time to come good but it is a restorable project... personally, id take this on as a project no problem but id want to snap this up under $1K... its close to the money already. Given title and effort, id be hesitant to pay more than around $800

sorry Gav but this BG is not avail here, I tried. But I have a spare now. Al, the other stuff you're spot on probably. I'd still like the apron to be included though.