I used redline synthetics in my differentials, transmission (manual), and transfer case. You can use MT90 for the tranny and transfer assuming you have a manual. For the front diff I used 75w-90ns and for the rear I used 75w-90. I don't have my manual but the service quantities are listed in the back of it. I believe it was a little over 2qts for both front and rear diffs and 1.5qts in the transfer. The tranny was somewhere around 4qts but I spilled quite a bit while filling.

Check out 4crawler for more info

As for a brake fluid flush, I have never heard of this before but I would not recommend this. He may have meant brake cleaner but I doubt he would use this on internals. Just ask him to drain and fill.