+1 what IndySteel said, this is the time to start looking for/riding with that saddle.

Do you know if you need the cutout? There is a test posted here on TE to help you determine that, if no one else has found it and posted the link I will find it tonight when I get in from my ride.

The SI Diva cutout is quite a bit longer and wider than the SE Lady (LDY) Gel Flow. Does your bike store allow you to demo saddles? Some do, this really helped me when I finally was riding long enough to realize my Brooks saddle wasn't going to hack it for me.

Good luck, and congratulations on your first tour! How long of a ride is it?