I think that is a lovely ring, and I really do enjoy white sapphires (and that setting is gorgeous). They are very white, and in certain lights may have a blue-ish, or almost lavender tint to them. A high quality sapphire will be very clear, although lower grades/cuts can look a little "cloudy" or "milky" at times. They give off plenty of "sparkle", and only a very little bit of "fire". Sapphires are very hard stones (about an 8 on the hardness scale), which makes them quite durable.
10k gold is actually an excellent choice for a ring you will be wearing every day... it has a lower gold content, making it much "harder", and will not scratch/dent/bend nearly so easily as a higher grade gold (like 14k) will. It can be sized just as easily as any other ring, by almost any jeweler.
As far as suggesting shopping together for your ring with your future fiancee, you can bring it up in a conversation about marriage if you wish ("I'd love to show you a few rings that I've seen that I like!" or something along those lines). Show him some of the rings that have caught your eye, even if it's just this one. If he sees how much you love this one, he'll probably go ahead with it. You'll still be surprised by the proposal, I'm sure... so it's not like you're ruining the thrill by helping him find the perfect ring. ;)