You probably won't need spacers for the chainring. On most conversions, the spacing seems better if you have the ring on the inside of the spider (where the small one is usually), so you should be fine.

As for your decision on the wheel, I think its a smart one. Cheap hubs have bad bearings and won't ride smooth and will need to be replaced all too quickly. Also, I have no idea what kind of cog and lockring they use, but remember, this wheel is also your brake. You will put your life in its hand and its not the place to skimp. The IRO is as low as I'd go quality-wise.