The fuel injector holders and injector o-rings might need attention. The o-rings are a PITA to install. About the only tools you need are an allen key/socket to release the injectors and a 12mm(?) flare wrench to remove the fuel lines. You might need new fuel line clips but you can order replacements later for the ones that break.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD