Hi
It does take some time to get the basal rates adjusted on a pump as although there is an adjustment guide, it's still going to be a bit trial and error in getting the rates adjusted correctly so for a few weeks you will need to test bg levels about twice during the night at different times so that the basal rate is at the right level.
As you will still have some Lantus active, it's probably better to eat a bit of carbohydrate before bed if that's what you would do if you tended to go low overnight unless your DSN has taken that into account and adjusted the basal downwards. Whether or not the basal is adjusted correctly will depend on bg testing. Once the Lantus has gone, it will be a lot easier to get the basal ok.