Just take your time and take a look at all the hoses real close - even under the hood. You don't have to go to MB to purchase the hose. Just take some in and match it up. Make sure you match it up for it's service too.

I would advise purchasing a little hand pumped vacuum pump. I think they are available at Wal Mart too. You can test each device that operates using vacuum with this thing. Also, you can purchase different types of vacuum hose fittings at a well stocked auto parts place to adapt to the different connectors on your car.
Take your time and you will be fine.
Jim
'85 300D
'95 E320
'97 CRV