After just changing all my fluids as well here is something that will help with the diff fluids. As for whether or not to drop the pan, well I would say yes. You never know what you might find in there. There is a magnet that collects all the real fine metals to prevent damage to the bands, drums, etc... If the magnet is covered it may not be doing its job and therefor damaging the transmission. The gasket is about $8 and the filter is about $14 and it takes only 20-30 min to change. As for the fluid change I would recommend doing a complete flush using the cooler lines and put in a good full synthetic. Valvoline has one called Valvoline Dextron IV ATF Multi-Import FULL SYNTHETIC that runs about $23 a galon and is compatible with the following:
- Toyota/Lexus - Type T, T-II, T-IV (except hybrids)
- Honda/Acura - ATF-Z1 (except CVT)
- Nissan/Infiniti - Matic-D, Matic-J, Matic-K (except CVT)
- Hyundai/Kia - SP-II, SP-III, SP-IV, Genuine ATF
- Mitsubishi - SP-II, SP-III, SP-IV
- Subaru - ATF-HP (except CVT)
- Mazda - M-III, M-V, JWS-3309
- BMW - LT 71141, LA 2634, 7045E
- Mercedes Benz - NAG-1, 236.10 and older
- Volkswagen/Audi - VW 052 162, 052 990, 055 025
- Volvo - 97340, 97341, 1161521
- Jaguar - JLM 20238
- Ford - Mercon V