Taking on the lawn but clueless!!!

Apodemus

I’d be wary of removing sand and replacing with manure. Sand is good for drainage and reduces moss problems, but it all depends on how dry or wet your garden and surrounding soil is. If you are in a very dry part of the country then you want more organic matter in the soil, in a wet part you want more sand.

Manure will introduce more weed seeds. While you can easily control the broad-leafed weeds later once the new turf is down, if coarser grasses seed themselves from the manure, the only way to get rid of them is to dig them individually by hand.