1337, you have a Mazda F5M, or F25M transmission in your protege. The difference is the F5M came with the SOHC engine and the F25M came with the DOHC engine. I believe you can swap the 5th gear from a Mazda 626, but that may be the G-series tranny instead of the F-series. I have the F25M in my MX-3, and plan on swapping in the transmission from a 1.5L SOHC Protege when I can afford to. The individual gears are the same, but the final drive is 3.4:1 instead of 4.1:1
I'll try to find the link I have for the Protege transmission info in a few minutes.
Cheers,
Vol
Edit//
Here's a link regarding swapping 5th gear in a Mazda F-series transmission
http://www.mx-3.com/phpBB3/viewtopic.php?f=24&t=65457
Hopefully, you won't need to be a member, and even though this isn't your car, the transmissions are the same for this procedure.
Best of luck!
Here's the link I was looking for...
http://www.protegefaq.net/transmission.html
Lots of great info here. Anything with an 'M' is a manual, anything with an 'A' is an automatic (in case you get easily confused like I do). Have fun!