1998 Forester- at oil temp flashes then stalls

I hit a rock and it dented the transmission cover- local mechanic replaced cover and the next day at oil temp goes on- car stalls this begins to happen intermittenly. Sometimes stalls then I can restart- at oil temp stays on. TRans fluid ok Then it began to stall all the time -had to have it towed 150 miles to Subaru Dealership. They want to replace air intake…something at the cost of $500.00 then they will look at codes related to transmission. This sounds crazy. Car was running fine before rock and transmisson cover was replaced. Help!