dirtmagurt

For this reaction http://i.imgur.com/Y2Y1c.png?1?5611 We have to show how it occurs and it has to be subsitution because we haven't "learned" elimination yet. By this I mean it is a practice question for a test coming up where elimination will not be tested. I am able to get one of the products, the product where the CH3 group is not inverted but I don't understand how to get the second product where the methyl is inverted. So I tried it again and I am not sure if this is correct but I wrote that the alcohol group on the Carbon that is also attached to a deterium gets protonated by the H3PO4. This makes h2O and h2Po4 and the H2O gets attacked by the nucleophilic OH (other alcohol) which makes an oxonium ion. The extra H+ then gets taken by the H2PO4 and that is one of the products? Is that correct because that is what my friend told me but I am not sure if it is correct or not and I was wondering if maybe this reaction has a hydride shift?