BMW Repair: camshaft positioning sensor, cam sensor, camshaft positioning sensor

Question
I need info regarding camshaft positioning sensor for a 2000 323i.  The light stays on and I'm told it is due to the camshaft positioning sensor which may or may not be malfunctioning.

I would like info including:

1) Symptoms

2) Easy of replacement - DIY?

3) Best place to purchase part

4) Other important info

The engine just started missing; could this be a symptom?

Thanks

Answer
I really need the exact code(s) to be sure but the cam sensor(s) are a common failure.
Get them fron the dealer.With a Bentley manual you should be able to DIY. No special tools.
If your engine uses both an intake and exhaust cam sensor replace them both.