2000 Maxima w/ 68k: do I need tuneup?

I'm the original owner of a Maxima 2000 GXE with about 68,000 miles.  I'm
seeking advice on how I should go about service.  I've had no work done
besides a recent radiator flush, new rear brakes, manual tranny fluid
replacement at 36k, all ignition coils replaced at 32k (under warranty).  

Stills runs fine.  But it occasionally misses when I first
start (then runs fine a few seconds later) and sometime she hesitates when
I punch it.   It is starting to "rumble" a bit so I'm guessing I have an
exhaust leak that needs addressing.

Would a tuneup accomplish anything?  Any other service items?  Spark plugs
don't need to be replaced, right?  

In the back of my mind is that my Maxima was flooded in the summer of
2006.  Several inches of standing water on the floor.  I shop-vacced every
day for about 15 days before I stopped pulling up water.  The mechanic
replaced a water-logged idler pulley, but otherwise he said no other
issues and that the engine is sealed. 16-months later, there is no
interior smell and no problems besides what I described above.  

Also my interior fan sounds like a Harley.  I suppose it is not easy to
access the interior fan?

Thanks,
Mike