Flywheel

Anyone here have any experience with a cracked flywheel? A day or so ago my truck started making a clicking noise. At first I thought it was the valves tapping but when I popped the hood I could tell that the noise wasn't coming from the top end. I took it to my regular mechanic who says he's 90% sure that it is a cracked flywheel. He owns a shop and has worked on and owned Chevy trucks all his life so I have no reason to doubt him. I was just hoping that maybe someone else has encountered this problem and can tell me a little about the symptons. I just can't shake the feeling that I'm about to spend alot of money replacing the engine in my truck.

If the flywheel is cracked, no mention of year here, the trans has to come out, how does that equate with a new engine.

If the flywheel is cracked, no mention of year here, the trans has to come out, how does that equate with a new engine.
It's '99 and if the flywheel is cracked then I wouldn't need a new engine. I'm just worried that maybe my buddy is wrong and that I'm about to spin a bearing which would equate to a new engine. I was just hoping that maybe someone else has experienced this same situation so I could compare symptoms.