The switch itself is not expensive, I am pretty sure it's <$50. However it is tricky to install due to the fact that it's secured to the distributor with a peened rivet (ie the pin is beaten with a hammer to compress it & wedge it into place). The tricky part is doing it without cracking the new switch, but it can be done. There are a couple of alternatives: junkyard distributor, but you may face the job again in fairly short order, or a new distributor complete with the switch. Last time I checked, about $300. A mechanic friend of mine routinely replaces just the switches, takes him about half an hour IIRC. Plenty of other bits of good advice in the other posts, and the first thing I'd do in your position is grab a spare spark plug, and next time the car won't start pull off a plug wire & stick your spare in there. Ground the plug & crank the engine to see if you've got spark. If there is spark then you need to look at the fuel system, not the hall switch. If no spark, I'd stand by my first guess - hall switch. They do eventually fail, and often it's pretty obvious when you take the distributor out & look at the wires - in many cases it's worn insulation shorting it out. Please do bear in mind though that my advice here is anecdotal as I've never had an LH2.2 car myself. Don't buy that $300 distributor based solely on my say-so! Good luck!
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Chris, Dartmouth NS Canada 70 M-B 280SE, 83 245DL, 84 244 turbo, 90 780 turbo, 92 VW Golf