this is a stock vibe no mods. any suggestions about "running the wires" is this a visual inspection or am i hooking a multimeter?

2004 fwd 70,000. cel came on before x-mas. car was professionally (paid $) diagnosed and they said it was the 1st O2 sensor (sensor 1 bank 1). I replaced the O2 sensor in the exhaust manifold with a Bosh, x-mas eve. drove the car from OH to Col and back about 2,500 mi. the cel came back on yesterday...