I'd have to concur with Fudman on this one, do one "major" thing at a time if you need to drive your card daily. The spark plugs can be done with the VANOS as you already have the coils off, plugs are simple screw out, torque in. The cooling system on the other hand is a seperate project. When you do the VANOS, you can keep all the coolant hoses connected except for the overflow tank which is the high point in the system anyways so where air will go. This means doing a VANOS does not require a cooling system bleed. Also, knowing how to spin off the fan / shroud from your VANOS experience will make the cooling system update that much easier.It takes me a LOT longer (like 100x longer) to do any job than you guys. Mostly I'm scared at first (unless I'm thrust into it as in the alternator).
In fact, I spent about 5 hours today finally repairing my trunk loom. The wires have been busted up and broken for, oh, I don't know how long, maybe a year? And I made a big mess of it all. Point is, it takes me a LONG time to do things, mostly because:
a) I have no clue what to do
b) I don't know which parts to buy
c) I don't know where to get a good price
d) I don't know if I'll have the right tools
e) I break a lot of things when I do do these jobs (it always happens)
f) I'm scared (see a, b, c, d, e, above).
So, yes, I WILL do my VANOS sometime. I already bought all the cooling system overhaul parts.
Q: Do you recommend doing the cooling system overhaul and VANOS and plugs at the same time?
Pretty much all e39's should have VANOS, Cooling System, CCV replaced by 100,000, each is a "day" job IMO. The CCV is next for me even though mine look mayo free at the valve cover connection, likely because I have a FL (hot) car.