The temp light came on because the fluid got too hot.  The OD light came on
becasue the computer locked out OD due to the excessive temperatures.

How black is it?  How long since it, and the filter, have been changed?

Never good...

Most likely something.  It's not the torque converter, as you said reverse
works.  I'd say the most likely explanation is that you burned up your rear
clutch.  It could be other causes (blown seal, valve body malfunction), but
something's causing the rear clutch to not engage.  It could also be a
busted front planetary, but that's a hard part, and pretty unlikely unless
you were using the truck for sled pulling competitions or some other such
abuse.  At a minimum, you need to drop the pan and see what kind of junk is
in there.  I'm betting you're going to find a good amount of metal shavings
and clutch material.

I hate to say it, but I think you just bought yourself a rebuild.

That's helpful....

[snip]

You'll get more flies with honey than with vinegar.  Tom must have a thick
skin; kudos to him for resisting responding in kind.  His advice was right
on the mark; I concur.
Bryan