Blauparts sells Ravenol transmission fluid. I haven't used it but maybe someone here knows more about it. They do have a pretty good writeup of the transmission service procedure. FWIW, I did use Ravenol BW44 transfer case fluid from them for my transfer case, as the oem Mopar BW44 fluid is on an extended backorder.
I recently did mine and wanted oem fluid, so I ended up getting my pan / filter from KLM Performance for $270 and there's a reseller on the Amazon Mopar store who sells the Mopar 8&9 speed fluid for $85 for a 6 pack. The pump is around $10 on Amazon. FWIW, the fluid from Amazon is the real thing, and I doubt you could find it cheaper anywhere else.
Mopar parts online sells the pan / filter for $295 in my area with a list price of $419 so your dealer price sounds a bit low from a dealer. Was that parts only (including fluid), or his price for the service? If it's for the complete service that sounds like an almost bargain
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