It all depends do you have a neww or classic caddy I have a classic very expencive to work parts are hard to get and when you find them bring your gold card new caddys not much better if have to ask you can't afford it no offence intended that's just the plain truth
E.G. If the underside is rusted to f**k then its going to be a toughy!
I know this kind of stuff because I help repair old VW Campers and Beatles.
Also I was wondering what you doing with it afterwards?
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Old = Expensive
Inbetween = Decent
New = Cheap
BS Story = Really Cheap