In reply to Stuyoung:
An opportunity to go climbing outdoors with an experienced partner is a great privilege for a beginner. In climbing you'll do well to grab these chances as often as possible, it'll be good for your climbing, and it'll be a great day.
What exactly is it that you're unsure about? If you can climb 6a indoors there's plenty of stuff for you to climb on the slate. If your experienced mate reckons yours up to it then you're up to it.
Basically stop f**king whining and man up, you'll be fine.