Welcome to Mercedesshop!
The noise from the valvetrain, I would venture to guess, is one or several hydraulic compensators. These are sort of like hydraulic lifters for an overhead cam engine. How many miles on the engine?
The starting concern could be worn or hardened valve stem seals, and or bad/worn/incorrect spark plugs. Use only the correct/recommended spark plugs in this engine, recommending the Bosch Super spark plugs. The hydraulic compensators and valve stem seals could be combined into one operation and some money could be saved, some work would be a duplication, such as removing the valve cover and removing the racker arm brackets.
On the fuel pump, they can get noisy with age, but I've known people to put up with the noise for thousands of miles and it'll still keep the pressure up. I think you could wait on that if you'd rather work on the engine noise and starting problem first.