Going to propose to my girlfriend of 5 years. Any advice?

I (29M) am planning to propose to my girlfriend (27F) of over 5 years. We met in college through mutual friends and just fell in love and never stopped. I know, it probably should’ve happened sooner but the timing never felt right… until now. I’ve picked the ring, the spot, the day. Everything’s set. And now that it’s getting closer, the nerves are kicking in.

Quick backstory: we’re both obsessed with history and horror. That’s always been our thing. A while back, she sent me a post on Instagram about a museum she really wanted to visit. That led me to the Vampire Museum in Doylestown PA. The second I looked into it, I just knew this was the place.

I reached out to the owner and he’s totally on board and super supportive. I told her I’m finally taking her to the museum and she’s so excited.

But now I’m kind of spiraling. I don’t know who to talk to about this so here I am. How do I calm these nerves? What should I say before I get down on one knee? Do you think she’s suspicious already? Should I suggest she wear something nice?

Any advice is appreciated. I just really want this to be perfect.

TL;DR Planning to propose to my girlfriend of five years at a museum, but I do not feel prepared at all.