You can remove the oil pan & front cover in the car but it isn't easy. Takes at least 10 hrs in the shop.
The lower guide rail should always be replaced, so you shouldn't worry about dropping the chain. Also the distributor drive gear may be worn as well.
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)