Can a princess setting be altered to hold a round stone?

[MichaelScott]

After some years of marriage, I think it's understandable that tastes change. We sort of always planned on upgrading her diamond when we had the income, and now seems like a good time. She currently has this setting with a 0.5 carat princess diamond.

http://www.samuelgordons.com/tacori-engagement-ring-2638-pr-45

Google has failed me on this question. Do you think that a jeweler could alter the prongs and put a round cut diamond ~0.75 carat in its place? Is that an extensive alteration to a ring? What should I expect to pay for something like this?

 

[04diamond<3]

I'd contact tacori about that...their settings are so intricately made that I'd want them to handle it. They may tell you to contact the authorized jeweler...but I would still check with them first.