When I rebuilt mine, I bought this trans rebuild kit
the listing shows it for both the A518 (46RE/RH) and A618 (47RE/RH, 48RE)
It has everything you need as far as steels and friction clutches, seals and o-rings. I needed hard parts for my overdrive. Unless you have a press and the proper tools, the average DIY'er won't be able to replace the clutches in the overdrive unit.
You can find some info from the pdf files here: