'96 SL1 Leaking Trans Fluid

My son's 125K+ mile SL1 has been leaking transmission fluid, but has just
started getting much worse. I took a quick look underneath and it appears
to be coming form the area of the filter, transmission cooler lines and a
sensor. I'm guessing it is one of the cooler line fittings since it appears
to be wet near that area.

Question: Is this a common leak and if so, will tightening the compression
nut on the cooler line stop it or is there an O-Ring in there that must be
replaced? Also, it appears that space is at a premium in that area so
swinging a wrench will be tough. I'm assuming that if the trans filter is
removed there will be enough space, but just wanted to check with someone
who may already have done this job.

Thanks in advance for your thoughts and advice. The car has been extremely
reliable and have only replaced a muffler in addition to regular maintenance
items in the 18 months he has driven it.

Bob