05 pathfinder problem?

hello, just got a 05 pathfinder, was reading about oil trans and antifreeze mixing up, the radiator has a milkshake color in the cap, trans i cant tell if there is any mix, looks just a little brown, and dont see any problem with the trans, but just a little kick when put on R, plus a little hard from P to R, did the bypass already...i fell like my mechanic is not update with the problem, he said looks ok, nissan guy said, ohh, may b good now, but is gonna get damage soon, i got a 3 month warranty on it, but i guess will get fix only if brake, is not nissan warranty, it has 96000 k, what should i do???????thanks...