My question is whether I should proactively replace my timing chain on my 87 300D?

History....
- 287K miles but overall runs pretty good.
- At 90k - timing chain replaced due to failure ($$$$)
- $$$$ of work done to keep this running over last 10 years (rebuilt IP, wheel bearings, rebuilt A/C compressor, etc, etc, etc)
- Now trans shifts very rough for last year and slow fluid leak due to seal(verified vac pressure to trans, etc.)

So....I am thinking about getting a rebuilt transmission but am getting concerned that if timing chain goes....then it becomes doorstop.
I have read forums and it seems there is not a concensus on how often to replace chain and whether to replace all of the rails and everything else.

Any opinions on what I should do?

__________________
Jeff L

1987 300D (277,000)
1995 E300 Diesel (122,000)