OK - but what problems are you having?  Why do you think the transmission is
"going out"?

That's a good finding.  Now you have something to go on.  This would be a
good place to start.

That could be too long of a list to put in a newsgroup post.  Better if you
would describe your problem.  But - you already have a trouble code - why
not address that instead of considering other things?

For pricing, you are better calling shops and telling them what you are
getting for a code.  References for a good mechanic are always more valuable
when they come from local people - preferably from people you know.  Call
the dealer - it's a good place to start when trying to understand what will
be done, and at what price.  The good news is that the dealer is always the
most expensive route, so you get past the sticker shock right up front.

All of that said - did you purchase the car new?  If so you have lots of
warranty left (probably) that will cover this repair.  If you bought it
used, you may still have warranty left that will cover it.  Post back with
whether you purchased it new or used and what mileage is on the car now.  If
it's under 60,000 miles, you can get the repair done under warranty -
assuming some issue with the car or the use/maintenance of the car does not
invalidate the warranty.

If your output speed sensor isn’t working properly, your transmission
cannot operate properly.  The output speed sensor is one of the
primary inputs used to determine when to shift.

The good news is that you probably only need a new output speed
sensor.