The changes are always dangerous when you have a good position in Google.
But I always think if you avoid touching the tag in the page type:
meta Title
meta Description
Meta Keywords (only if you were already there!)
and finally, I would not change the content at the top of the page but only the graphic design.
I was afraid too when i did the same for many customers, but i did always so and never i lost a positions
Ciao
Maurizio