When I changed the filter, it cost me something like $20. (Can't rember the exact amount)
If you're really tight on cash, you may be able to reuse your transmission fluid (assuming it's not contaminated with debris) and pan gasket (assuming it's not cracked).
Change the filter yourself, it's a 30 min job max.
1. Drain the old transmission oil (5 min)
2. Remove the transmissin pan (5 min)
3. Remove the transmission filter (5 min)
4. Replace the transmission filter (5 min)
5. Replace the transmission pan (5 min)
6. Replace the transmission oil (5 min)
You need a 10mm & 14mm (I think) socket wrench and a phillip screwdriver.
Easy and quick job...my sister could do this....then again my sister is a certified MB mechanic. hehehe. just kidding. My point is: change the filter, it's cheap and easy to do. Don't waste your time with the gunk remover...that's just a temporary fix.
Good luck.
jrmd01@yahoo.com