Garmin Ver5 lite

My new Garmin GPS 64x comes preloaded with Topo Ver5, but does not cover what v5 lite does, (Apparently 20 m contours against 50m, and the lite version apparently has farm boundaries which I am particularly interested in), so I have to purchase the lite version. My question, is there enough space in the memory or will I lose the preloaded Topo maps. I have contacted Garmin, but are slow to respond.