Just a thought, if the oil changes were neglected I'd imagine all other fluids throughout the car were neglected. Spend the $$ and have all fluids changed and then use a regular schedule to change fluids.
That ticking noise can be caused by the oil check valve, also the cause for the low oil pressure. Do a search and you should find plent of info. Oil pressure in these engines also varies significantly with various oil viscosities. Look in the manual for recommended oil viscosities vs outside temperature.
02 C32 AMG
84 190E 2.3 5 Spd