Step #1--Ignore this mechanic, and never darken his door again. While he is correct that Hondas of this vintage have known serious transmission issues, his statement is more representative of an "Old Wives Tale" than it is of technical knowledge.
Step#2--Take the car to an independent transmission shop (NOT AAMCO, Lee Myles, Cottman, Mr. Transmission, or any other chain operation) and have them change the trans fluid and filter.
Step #3--Do a lot of praying that your transmission continues to operate.
No--not because the fluid was changed, but because this VERY belated maintenance may not be enough to save any 10 year old unmaintained transmission, no less one from a model with a history of transmission issues.
Please note--I really don't know how to correctly interpret some of the wording in your post ["...if your transmission fluid has never been changed (which I'm almost positive mine has)"]. I'm not completely sure what you are trying to tell us with that statement.
If you are telling us that you are not sure if the fluid has ever been changed, that is not a good sign.
On the other hand, if you think that it was changed some time in the distant past, but that you can't remember when, that is really not much better. Trans fluid needs to be changed every 30k miles or 3 years (whichever comes first), and failure to do that is the sure way to send a transmission to an early grave.
Do you have any maintenance records to refer to, regarding when this trans was serviced over the past decade? It should have been serviced 3 times so far.