Resizing Platinum Rings

I need to get my platinum engagement ring & wedding band re-sized (made larger). They are contemporary in style and have a sand-blasted finish with diamonds scattered on both rings. I really don't know much about the process and was wondering how easy it will be to get done. I heard that platinum is not easy to work with and can be complicated. I don't want to ruin the design of my ring. Any suggestions?

Thanks,
Renee