The most important thing when choosing the right Rim is to pay attention to the number of holes. No matter if there are 32, 36 or 48 holes, the number should correspond to your hub. Rims with a welded connection are more stable, those with a plugged connection are cheaper. The so-called Aero Rims have rounded sidewalls and cannot be ridden with breakes. When it comes to weight you can say that the heavier the rim, the more stable it is. So when you like to do Bomb Drops or if you don't ride that clean yet then you shouldn't take the lightest rim.
For the assembly we recommend a Spoke Spanner.