I'd probably give the go ahead on the differential seals (assuming that's what he means by front axle O-rings), but wouldn't let him fool with the front main. You can buy a lot of spare quarts of engine oil for the price of that front main seal repair.

My guy suggested replacing my oil pan gasket and rear main seal for $1850 to address "seepage". At my current oil consumption rate, I can go for another 285,493 miles before I break even!

2002 X5 3.0 242,000 miles
2004 325i 107,000 miles