If the fluid was in that bad a condition, you may be SOL. I'd think you could change the solenoids yourself by dropping the valve body but I'm not familiar enough with this transmission to be sure.
If you're really wanting to try everything before doing anything more in-depth, buy a couple bottles of this:
http://cgi.ebay.com/ebaymotors/LUBE...ptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories
Drain the fluid a bit to prevent overfilling, put a bottle in and drive it around as much as possible. Results may take up to a few hundred miles but I've heard some miracle stories about this stuff from people who I trust with trannys in bad condition. If it does help at all, drain the fluid in about 1k miles and refill along with another bottle. Failing that however, mechanical work is in order.
FYI, changing the fluid on a regular basis probably would have prevented this. Learn from your mistake and don't go any longer than 30k before changing your fluid. Drain and refills every 10-15k would be well enough until about 100k when you should drop the pan and change the filter.
FYI to everyone else; Mazda M-V is NOT NOT NOT equivalent to Mercon V. Some have used Mercon V without issue but its not ideal. M-V is equivalent to Dexron-III, and Mercon V does NOT back-spec to Dexron III. Castrol Import Multi-Vehicle does but IMO, is a bit of a waste of money. It works beautifully for where Toyota T-IV and the like is spec'd though. For M-V, any "Dex-Merc" will be fine unless you want to go the extra mile and get a synthetic fluid.
