1999 Jeep Cherokee Sport P0138 P0455

Here's the scoop: 1999 Jeep Cherokee Sport, 115K miles, basically ran well. Check engine light came on, took it to autozone, it was p0138 downstream o2 sensor. I replaced that, turned off the light, ran well for a few days, until today. Shortly after a cold start, the light came on again, this time the engine started running rough and I smelled raw fuel vapor. I took it to get scanned again, this time I get p0138 as well as p0455 major evap leak. I poked around, found a leaky vacuum line, replaced it, but still runs bad. Anyone have any idea if the two codes are related in some way? I'm going to look for more leaks tomorrow. thanks for the help.

either the circuit to the 02 is nfg or the sensor from the Zone is NFG!