I would contact GAHH in California and get there input on the Hides you will need. I just stated on my 280se 111 Cabriolet and I needed 3 hides to do the door panels, dash, kick panels, rear quarter panels and top boot. But 280se are larger than 113 cars. Of course you buy the seats, headrests and armrests as kits. It does not make sense to duplicate them in the field. Then you need 3M sprayable contact cement with a cheap paint gun. I don't use the stuff in the can...its ok for carpets but once hot from climate it tends to lose its grip.
Good luck,
Eric
70 280se Cab 111.025
Former 113 owner