Help with leaves and mulch?

Im a brand new homeowner and have no clue about planting or taking care of a yard. The front and sides of the house has 3 trees, a few shrubs, and different types of flower bushes but I dont know the names of everything. The previous owner must have put a layer of plastic wood mulch (I am learning mulch helps the plants, its not just to make the area look nice). My question is, its messy under the bushes, around the flowers due to mixture of leaves, old mulch and dirt. The leaves arent mulched up they are just from falling from the trees last season. They are even like stuck into the root areas of the plants. Is it ok to leave the leaves there and put wood mulch on top of them, or should they be removed (which will take forever since its a big house and its all the way around)? Sorry I really have no clue about this stuff. Also do you think these trees are too close to the house? a href="http://jen22t.shutterfly.com/" rel="nofollow"http://jen22t.shutterfly.com//a