240D - timing chain tensioner and rail

I've got an '83 240D with 243,000 miles that has some pretty bad timing chain slap. I'm planning on replacing the tensioner soon. Does anyone have any advice on this job? Yes, I have the service manual. It looks pretty easy.

How do I know if I need to replace the tensioner rail as well? My mechanic mentioned that the plastic rail might be in bad shape due to the chain slap, especially since I've had that problem for a while. I really don't
want to have to replace the tensioner rail, since it looks like a helluva job.. according to the service manual "Step 1: remove radiator and fan." Ack. But if it needs replacing, so be it. How do I tell?

Also, should I consider replacing the timing chain? How do I know if it needs replacing? From what I've heard, timing chains generally don't need replacing, but if I've had pretty bad chain slap for a long time then mine
might be damaged. How can I tell? I certainly don't want to leave it alone, then later find out (the hard way!) that I should have replaced it.

Thanks in advance.

- Nathan
'83 240D, 243,000 miles