stumped ! O2 sensors

Just given a cherry 92 Grand Marquis with 19000 miles . It's been running a little rough so hooked up a scanner and got a 177 code ( up stream O2 sen. ) . No big deal . Down to the parts house and picked two up . Here is where the fun began .... How in gods name do you access the electrical connection ? I assume I can get to the sensor plug through the wheel well but when it comes to the elect. end I'm stumped ....... feel like a bear driving a Studebaker . Thanks in advance .