It's ok to be nervous when delving into something new. Think about the positive things you know about the situation and focus on them. You can even make a list if you want.

For example, we know Ash & Magnolia have many years of experience under their belts, as well as many loyal customers. This would imply they know what they're doing.

And from what you said, you practice Wicca. So you're probably not an amateur to protection methods yourself?

We can also gather that despite your Christian upbringing, "God" hasn't struck you down for changing faiths. So why would this be any different?

If at the end of coming up with positive stuff, you're still scared, it's ok to decide it isn't for you. We all go at our own pace. Best of luck either way!