So you want to spend upwards of $200- on a bike that cost a bit over $100- new, and has never appreciated? You choice.
How do you know the OLD? Measure it.
Modifications:
new wheels
new brakes
new tires
at the same time you should get:
new freewheel (finding freehubs less than 130mm is very difficult and $$$).
new chain
new tubes
ISO630 tire selection is very good, though it takes a few extra minutes - not a reasonable reason to change to ISO622.
Get your self a set of these:
http://www.amazon.com/Avenir-Discovery-Road-Tires-Black/dp/B00165TW7U/
If you still want to do it;
1. measure your OLD.
2. measure the brake reach required with your current ISO630 rims.
hint: Google "Sheldon Brown O.L.D." and "Sheldon Brown Reach"
With the above information, you can go about selecting wheels and brakes.
For ISO622 rims, you will need brakes with 4mm more reach than you measured with your current rims. Most likely Tektro R556 will work. You will need to get "nutted" versions of the brakes, or drill your bike frame for recessed (not for the faint hearted, and make sure you use a good drill stop - test it).
Next to the wheels: machine built (cheap, spokes fail); custom (expensive, but done right - I recommend Peter White) or my choice - build my own (done right, no spoke failures, and not as expensive as custom, but more expensive the machine built).
Peter White has some 32h Shimano Freehubs with 126mm OLD, he will sell only as a pair of hubs or as part of a pair of wheels. I have heard that he is several months back ordered on his custom wheels. If I recall correctly, I will sell the hubset (front and rear) for around $75- (pretty sure less than $100- anyway).
Alternately, you can re-use your current hubs (does not make sense financially, unless you build your own, and many wheel builders will not use old hubs dues to liability).
Rims - my current favorite narrower (but not really narrow) rim is the Sun CR18 - depending on size they run in the $25- to $30- each range.
Spokes: like Peter White, Wheelsmith is my preference. I use SS14 spokes For a set of wheels, you will most likely need three different lengths: front, left rear and right rear. Sometimes you luck out and the front and left rear are the same. $25- per package, plus $10- for nipples.