Gun parts can be shipped into CA (resident address) without problems. Magazines can be shipped into California as long as they are 10 Round Compliant (There are companies that can convert standard capacity magazines to 10 rounders and ship into California).
All Firearms that are transferred to a CA resident have to be transferred via a CA FFL
All ammunition that is transferred to a CA resident have to be transfered via a CA FFL
All Pistols that are outside of CA borders have to be on the CA Pistol roster to be transferred to a CA FFL unless there are special conditions followed
All new Rifles in CA must not be considered an Assault Weapon (look up the special CA guide on this there is a flow chart), if the rifle you have violates this look into featureless conversions.
All Rifles in CA must be over 32 inches long and have a fixed stock.
All Pistols in CA can have neither a threaded barrel of shoulder stock (Pistol braces are ok, but questionable).