As for the oil pan, you're already doing a decent fraction of the work.

The real challenge with getting this done in 3 days is making sure you have all the parts available. You can comfortably do the work if you don't need to order anything. If you do, you're screwed.

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2011 M3
2006 Sierra 2500HD 4WD LBZ/Allison
2004 X5 3.0i 6MT
1995 M3 S50B32
1990 325is
1989 M3 S54B32

Hers:
1989 325iX
1996 911 Turbo