2004 Subaru Forester New Rec and Pinion, But Still Problems

Some months ago, I took my car to a mechanic because I thought it was leaking oil. The mechanic said it was leaking transmission fluid and that the rec and pinion needed to be rebuilt. (I had absolutely no steering problems, but I know nothing about cars). The car continues to leak fluiid--dark brownish--after the rec and pinion work. The mechanic said I just needed to continue driving it for a while and the leaking would stop. He said it was normal for leakage to happen with rec and pinion work, but it would stop. It hasn't. (I have to put a metal tray under it when I park the car in my driveway). Don't know if it's related, but the sometimes the car stalls just as it's started or at a stop sign. (It never stalls on the freeway). The stalling just started within the last couple of weeks. Thank you for any advice that can offered about the problem.