No, No, No, a thousand times NO!! Don't use ROM Manager. It does not work properly anymore. Please please use one of the alternate methods of flashing recovery, and for most reliable results, use Amon Ra, not Clockwork. Clockwork has developed an unreliable track record with alternate ROMs of late. A little research will show that there are many reported issues with both ROM Manager and Clockwork.
Velocity would probably be the best choice for you at this time, simply because the Froyo version is not really ready for use by the casual user. Also, take a look at Punisher v0.1 or Raptor v0.1. Both of those are very good ROMs as well.
And good luck to you. I hope you have as much fun learning all this as I have had. And the guys here and particularly on the IRC channel are always ready and willing to help you out should you get into trouble.