maintenance costs

As you can tell from the title I have an SL55 which for various reasons has been sitting in my drive for around 6 years. I work on cars myself however this is an entirely new beast with the SBC and ABC, correct me if i'm wrong but i think those are the right terms. Anyways, what would it take...

I am considering getting a high mileage (100K) S-Class. I would be grateful for any information about likely maintenance costs please? For instance: 1. What are the costs of components like tyres and exhausts which have to be replaced? 2. What do likely spare parts, like alternators, cost? 3...