Change front and rear gear oil and transfer case fluid of Jeep GC 2001
Asked around and found some possible solutions to extract the rounded-off plug:
1. Use a cold-chisel and hammer it into the female drain plug and make a notch in it. Then use visegrips to turn the chisel and take out the damaged drain plug;
2. Welder a regular square male bolt into the female plug. Use wrenches to unbolts it;
3. Use a special tool called Pipe Nipple Extractors. They are available at Princess Auto in Canada and Harbor Freight Tools in the US.
Too bad my Jeep is sleeping at the parking lot and I have to buy tools taking Bus.
Update: I had to spend 30 bucks to ask a garage to weld a regular male bolt into the female plug. I replaced the damaged bolts.