Vinyl siding over asphalt shingles? How hard?

I'm thinking about buying a fixer-upper and installing new windows and siding. The house is built into a hill so the 1st story is cement, the 2nd story is stucco with some T-111 on the back side of the house. I'm thinking the easiest way to reside would be to throw up some nailers and insulation, and install siding off of that, or would it be easier just to nail siding to existing combination of sidings? thanks, dan

general question in regards to siding preferences thats right, im all about opinion on this one guys...... i personally dislike the vinyl siding on my current home (not bad job on install just taste) i think the utility and j channel around windows and doors is just ugly as sin. i tend to watch a lot of the home shows on the weekends here in west michigan and have seen much in the way of siding that has the look of wood with much better endurance due to new composite materials. i really like the looks i have this product provide and have heard it is half the cost of real wood siding, but i know little of the costs of either. does anyone have experiences that could help?? i have done some vinyl siding at my place of emplyment (not like contractor or anything, was one small building) and was not satisfied with finished product (once again referring to aesthetics of the exterior finish)