Mercedes Electronic Parts Catalog on-line
EPCnet Online - Subscription Step 1 of 3
Go to the 2nd page and select the US option, if you have a US spec car and it'll cost you $0 for 12 months
If you have a non US model it'll cost $12 for the 12 months.
You'll be asked to input a CC info but that is for address verification only with the US option.
IMPORTANT NOTICE -- I don't know how this works if your address is not US based