just looking for general comments and suggestions about replacing the belt tensioner and belt for a 93 190E 2.6 with the M103 motor.

replacing it because its been rainy lately in sunny socal and it left my car with a squeaking noise around the belt. I inspected the belt and saw that it was cracked all over along the ribs and when I checked the tensioner, the pointer was way past the triangle/max point. because of this, I have a feeling that if I just replace the belt, I wont be able to tension the belt properly.

how is the space available to work with in that area for replacing the parts? do I need to remove the radiator on a 190E? and what is the sealant that I am reading in the FSM? i heard something about an O-ring? is there a part number available I can look up?