On whether to buy a new wheel -- yes. Dyno hubs are solid, but their dimensions probably don't match your existing hub. So you'll have to buy new spokes, a new hub, and either pay someone (or DIY) to take the old rim off the existing wheel before you can start building a new wheel. You can probably find a rim in the $30 range, and that's cheaper than paying for a builder's time to take the old wheel apart.

Plus you'll have a spare wheel if you need one.