I have a vacuum pump you can borrow if you need. There are definitely more than 2 o-rings in the system unless Mazda switched hoses and lines between '92 and '94. I recall there being an o-ring at every point where hoses/hard lines connect. The evaporator can be removed/replaced without removing the dash. I did it 2 months ago. It was a PITA, but possible.
'92
Interesting. Mine had o-rings at the compressor, where the lines attached to the condenser, at the receiver drier, and at the firewall.
'92