Oil leak, rear intake..clean & silicone ?

Intakes are easy... I've also used a new trash bag in a box to catch coolant. Then you just pull the bag out, trim a corner, and dump it back in. Or you can drain and run through a coffee filter or rag to make sure nothing bad gets in there. You have to clean the surfaces perfectly - no oil residue anywhere even from your skin if you want silicone to seal and work as a gasket.