i made a crown which i dont like for Sunday, can i make one tonight and be ready for Sunday as a cake topper?

YES

If its gum paste you have enough time, note for next time, make extras, as back up. When I'm pressed for time I put my pieces into the oven with the light bulb on only. DO NOT TURN ON THE OVEN. The heat from the light bulb helps dry the pieces. Place it on a cookie sheet lined with parchment paper.

If its all fondant, knead in a pinch of tylose powder into the fondant, this will help it harden and place in oven to dry ( refer to the directions above) HTH.

The ratio of tylose to fondant is 2 tsp - 1lb fondant, this I learned on a thread here from costumeczar, and it works for me everytime. hth

thanks a lot,  I've heard about the oven, that's where i store all my pieces. when it comes to Tylose, i didn't know how much to add so i just keep adding tylose, lol. thanks!

You're welcome

When I am working with a small piece of fondant I just sprinkle the tylose on my surface, dusting the surface like if you were kneading bread. You will feel the difference as you knead it in.  A little goes a long way.

Remember we are own worst critics, we see the flaws in our own work, where others see a beautiful yummy cake.

A completely different way to go is with modeling chocolate which firms up as soon as it's cold.  I does not hold up as well as fondant if it's going to be outside in warm weather.

How do I transfer the cake with a modelling chocolate tiara?

Do you mean deliver the cake?  I would put the cake and tiara in separate boxes and then put the tiara on the cake at the venue.