Two U.S. wrestlers in the second group won the first matches in their pool at the 2001 Greco-Roman World Championships in Patras, Greece Friday.       2000 Olympian Jim Gruenwald (Colorado Springs, Colo./Sunkist Kids) won his first match at 58 kg with a 3-2 decision over Ruslan Khakymov of Ukraine. Gruenwald was down 0-2 at the break and came out in the second period with a takedown and gut wrench to give him the win. He will faceTomas Kathan of Austria in his next match. "That was a tough first round match," said Gruenwald. "This year I kind of took a different approach to my training with the help of coaches like Momir Petkovic and Dan Chandler. They really pushed me to take more of a break before coming in here, so I come in here feeling like Superman. I started off this first match a little slow, but after about 45 seconds, I felt great and I knew that I had a lot left to give at the end of that match."     2000 Olympic champion Rulon Gardner (Colorado Springs, Colo./Sunkist Kids) decisioned Yuriy Yevseychyk of Israel 3-0 to win his first match. He will take on Georgiy Soldadse of Ukraine in his next match. "Against Soldadse I will need to really get into his face and get him tired early," said Gardner. "I'll try to get him off balance and not let him get his legs under him. I do feel some pressure, but not because I'm the reigning champion but because I have a tough pool."     Marcel Cooper (Triangle, Va./U.S. Marine Corps) started his first match well at 69 kg against 1997 and 1999 world champion Son Sang Pil of Korea scoring points off an escape and a takedown, but with ten seconds left in the first period Sang Pil threw him for four points. Cooper wasn't able to score in the second period and lost a 6-2 decision. Next up in his pool is Velin Marinov of Bulgaria.     Matt Lindland had a bye this first round and will face Bojan Mijatov of Yugoslavia tonight.    In other action, at 58 kg 1996 and 2000 olympic champion Armen Nazarian of Bulgaria had an explosive back-and-forth match against former world champion and 1999 world bronze medalist Alfred Ter-Mrkrtchyan of Germany. Nazarian was ahead 9-7 and ended up winning by injury default at 4:50 over Ter-Mrkrtchyan who hurt his rib during the match.    2001 Greco-Roman World Championships    Patras, Greece, Dimitrios Tofalos Arena    58 kg    Jim Gruenwald, Colorado Springs, Colo. (Sunkist Kids);  dec. Ruslan Khakymov (Ukraine), 3-2    69 kg    Marcel Cooper, Triangle, Va. (U.S. Marine Corps); lost dec. to Son Sang Pil (Korea), 6-2;     85 kg    Matt Lindland, Oregon City, Ore. (Sunkist Kids);      130 kg    Rulon Gardner, Colorado Springs, Colo. (Sunkist Kids); dec. Yuriy Yevseychyk (Israel), 3-0