1998 Ford Windstar oil in anti freeze reserve tank

Oil found in my anti freeze reserve tank. This has been an reoccuring problem. I recently had my coolant system flushed, and my reserve tank cleaned.

I've recently had problems with my engine not starting. It would kick over strong but not start. One technician replaced my alerinator, and it worked for about 5/6 days, then another tech. Replaced fuel pump. There seems to be hesitation when I first apply the accelerator.

My vents also don't work, No air comes out of any of my floor or dash board vents, only my defrost.