Mercedesbass

Hi i need help. im wanting to do a big 3 upgrade for my power wires on my C180 Kompressor 2003 saloon..so could do with some advice on how to get to and upgrade the cables to and from the alternator. I cant seem to find any posts or videos to help me. I have good electrical wiring skills ive installed many amp wiring kits but this is my first attempt at the big 3. And this car is going to have my biggest and loudest set up. To date so any tips and advice would be greatly appreciated