With your difficulty skiing then my experience may not be relevant but if you exagerated then you should pick it up quickly.
I picked up snowboarding quickly. One decent lesson and I was comfortable pretty much anywhere I went. I found that a lot of the skills carried over from skiing, edge control, comfort at speed, balance.
If it is just fear holding you back then don't fear the snowboard. Snowboards are like dogs, they can smell fear and it will smash you. You have to be aggressive (within your limits obviously.)
Momentum is your friend. You will never learn to ride unless you get enough speed up to actually get over the edge and turn. Once you do that you own the mountain and it's just a matter of progression which I expect is more difficult but heaps of fun.