Ticking is probably a bad cam lobe (or a few). Had a roasted cam on my m117 (similar engine). Ticked like mad. My m117 still ticks but that's a leaky exhaust manifold... stops if I unplug the #6 injector.

If you replace the cams, replace the rockers and towers as well. The towers are likely worn if the cams are, and the rockers definitely are. Check out one of my first threads here:
http://www.peachparts.com/shopforum/showthread.php?t=65460

A double-row timing chain has never snapped on an m116 or m117 engine to my knowledge. Yours is likely double-row. What does happen is the guide rail breaks (due to a combination of rail age and timing chain slack). This causes the chain to skip a tooth (or more) on the cam sprocket. Replacing your rails (about $50 and 6 hours DIY labor for a beginner who barely knows how to change oil) can save your engine's life. But it wouldnt tick.