I'm not sure if this would apply to your car, but my brother just had his timing chain done, not sure if rails and tensioner needed, but he spent only $500.00 on a 1985 380sl.
But that is here in los angeles.
I think he only had a new chain put in
'92 300CE - Sold
2004 C240 - C7 Wheels
2015 ML350 - P1, Pano, Ash poplar wood, Sport Dinamica interior, Running Boards Keyless go.