Boyfriend wants me to eat his ass

Imma start by saying I have never EVER! eaten ass. Last night my boyfriend told me that he wants to try new things in bed which happened to include rimming.. this is a HUGE surprise because he never liked “butt stuff” but now he’s asking me if I would be willing to rim him. I said yes but kind of turned off by the idea.

What should I expect?? Is it a pleasant experience or..