Will lip repositioning surgery (for gummy smile) change the shape of my lip in anyway? Especially when I rest my face.

I appreciate your concerns Tinafey, however photos would be helpful to answer your question in a more detailed fashion.
A gummy smile can be caused by several factors and treatments vary. Sometimes just a small amount of Botox can be an excellent option. If your lips are extremely large, lip reduction surgery works well. Lip repositioning surgery with lip muscle division can be a tricky option depending upon which technique is used and which muscles are divided. Come see me or another board-certified plastic surgeon in our area to explore the best options for you. Good luck.

The shape of the lip does not change after the surgery for the gummy smile. It just brings the inside attachment of the lip lower on the gums to cover more of your gums and teeth.
Regards
Dr J