The great advertisement for not being circumcised is that the sex is supposed to be better, since the penis is more sensitive. If you are concerned that at first it will be TOO sensitive (and for other reasons), use a lubricated condom. The lubrication will ease entry so you won't have to push so hard that it feels painful to you and her, and the condom will protect the penis head from being so sensitive that *bang* you're all done. Try not to be nervous (I know, easier said than done), you'll do fine.
Don't worry! My husband is uncircumcized, and we have an excellent sex life. He has never complained of pain or irritation. However, even after 14 years, he remains sensitive. But the good thing is, we can always do it again, and there are other ways of getting satisfied, too.