$3000+ to replace the guides. If you don't do it, chain slap may cause the engine to jump timing and then you be in it for bent valves.
Run, don't walk away from that deal not unless you're a DIYer and the seller is asking under 5,000 for it.
Here's a guy about to start on the repair.
http://forums.pelicanparts.com/bmw-5-series-e28-e34-e39/737894-m62tu-timining-chain-rail-failure.html