Re: Lead Paint
In addition to what ordjen said, vinyl siding IS NOT waterproof, it only sheds water, which means that you want the existing siding intact and weather resistant if you're going to use a topical product like vinyl or aluminum siding.
The difference between water proof and shedding water is this. Water proof means that water cannot enter the structure, period! Most conventional sidings are considered waterproof because without extreme circumstances, it keeps water out. Vinyl and aluminum siding, on the other hand, are only designed to shed water that lands on the surface and drops off. If water hits from a side or upwards angle, it will easily penetrate behind the siding and caus damage to the substrate.
The last thing I'll say on the subject is that while vinyl siding might look relatively good when first installed, it doesn't stay that way for long, and if it's damaged in any way - a very common occurance - you'll have no recourse because there will be no replacement materials available due to the fact that the product style and dimension changes faster than you can write the check to pay for it. A vinyl sided home also has less value come resale time than a conventionally sided home. IMHO, you're much better off to deal with your existing siding than to cover it up with something that will only promote the degradation of your home.
I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!