Honda Civic 1998 AC problem

Mileage: 140,000 miles
Engine: 1.6L
Transmission: Manual
Front Wheel Drive

I bought my car like one month ago. Only had the oil changed. Recently, I found the AC doesn't work very well, so I added refrigerant myself. During the first drive after that, when I stopped at the stop sign, something like smoke coming out from behind the car. The sound seems like a leakage, but i'm not sure. Anyway, it was a lot of smoke. And when I started moving, trying to switch to 2nd gear, the car dies, and I had to turn it on again. 30 minutes later, when I tried runing it again, it works find. But the smoke came out again the next day, although the car doesn't die this time.

Is this going to be a expensive repair?