valley pan gasket will cost you $2-3k. it's a slow coolant leak so I don't think it'll fry your engine if you heed the low coolant warning. I replaced it myself on our former 2002 4.4.

as for transmission fluid. I drained/filled the pan every other oil change after 50k miles.

we traded our 2002 x5 4.4 @ 170k miles for a 2008 4.8 last dec.

I replaced the entire cooling system/hoses, valley pan, alternator, WP, oil seperator, etc. the transmission was hanging in there...

Would the Valley Pan issue from the old 4.4 really carry over to the 4.8 ? I would think since they are separate motors you can't draw that conclusion. If anything, the 50i might have the issue since it's a 4.4.

no valley pan leakage possible? that sounds good to me!

I'm looking at moving up to an e70 too and kind of curious. FWIW - I had my valley pan and coolant system all done for just shy of $1000 last year on the 4.4 but that was an indie shop.