Well, after some conversations with Mark Hayter, I figured out what
needed to be done to the Shark to make it IrDA-compatible.

I replaced the current consumer IR receptor with a Sharp IS1U20.
This is also a three pin part, but the pin order is different so
it required some creative lead bending to get it to work right.
I also needed to remove the pull-up resistor (#566 on the parts
layout, the one closest to the receptor module).  I got the parts
as sample parts from a local Sharp representative, so I don't know
of a "real" distributor for them.

With that and a few changes to the com driver, I was able to send
and receive IrDA between my Shark and my laptop all the way up to
115,200 kbps (the Super I/O chip on the Shark can't do any of the
faster IrDA modulations).

If anyone is interested I can provide more details, but it was
actually pretty easy ... the hardest part was removing the old
module.  The changes to the com driver are pretty minor, but right
now it's a horrible hack (probe for the Super I/O chip, and hardwire
it to IrDA mode).

Thanks again to Mark Hayter for the valuable tips!

--Ken