E39 touring or Magnum???

Congrats on the purchase. You won't be disappointed with the Touring. Everyone pokes fun at the 525, especially in the Touring, but for me it was an easy choice. The V8 is great, but we drive way too many miles for sub 20 mpg gas mileage. Ours has been pretty good. The major items were the front suspension (complete overhaul) - $2400 parts and labor and the cooling system - $1400 parts and labor. Other than that, I had to rebuild my ABS controller, replace the subframe bushings, replace the smog pump, and replace the valve cover gasket. All that in 100k miles. I don't think that's bad at all. I'm pretty confident turning a wrench, but there are some things I'd rather leave to the pros (like the two above). The E39 is very easy to work on. You mentioned an oil leak. If you smell it burning it's very likely that it's the VCG. I replaced mine a few weeks ago and replaced one on an E46 today. Piece of cake if you ask me.

You'll also definitely want to do the subframe bushings on the Touring assuming it rides rough (which it probably does). It's not the shocks. There are four large liquid filled bushings that isolate the rear suspension, but they end up leaking and failing. They now make a solid bushing to replace it. Less than $300 for parts and you can rent the special tool from jase005 on here for $50. Not a bad job and huge bang for the buck.

Welcome to the club! Looking forward to seeing you around here.