Gasket sets are available. Everything else has to be bought as necessary. Many of the parts are made to repair sizes and the the whole job is a series of individual decisions and repair operations.
The parts that are necessary are greatly determined by whats has happened to the unit and how old it is. I have been working on MB V8s since 1973 (done hundreds of valve jobs). I have yet to see one wear out. I have seen them broken. Unless the motor has sat for years with water in it the only thing wrong with it is probably heads/valves/chain related.
Bosch Master, ASE Master, L1
33 years MB technician