Single mass fly wheel and clutch
 

so I'm pretty sure I'm hearing the death sounds of my fly wheel from what I've heard people say it sounds like. I have a used one that I want to swap in but I dont want to swap a bad one. So what should I look for on the used one before I put it in? Is there a specific area that cracks or warps? Also the dude at the parts store said I need to know how many teeth are on my fly wheel so I can get the alignment tool for the clutch. Anyone know this or where I can find it or a part number for the tool? Thanks for the help

Tool is couple bucks for most auto stores. # FT75 stamped on it. Should be same as all other zf-5 clutch alignment tools