Once you have the radiator out, the water pump should be easily accessable (though I've never done it on an X5, just e30/e36/e34/e46.

I've never had to do the valley pan gasket (knocking on wood as I type) so I don't know how hard it is. I'm sure others will chime in.

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Kirk
Las Vegas
2016 X5 40e Mineral White/Black Dakota Leather, ZLL, ZCW, ZDA, ZDB, ZPP, multi contour seats, rear side window shades, HK stereo
2011 E90M3, 6-speed manual