what do i do when i can't unplug?

trying to replace an oxygen sensor, and have a problem i've never encountered before. i just can't get the wire unplugged. ok, to clarify, this is on the wife's toyota not on either of my bmw's, but
toyota folks are so less helpful, i figured i'd cross post here as well.
anyway, the sensor is on an '02 with 85k miles, and doubtless original. on the toyota it's in one of those places where you're lucky to get a hand on the connector, i can't see how to get two (at least of my hams, and the wife, tho petite, isn't about to lend a hand, sorry for that). so i'm trying to yank the thing apart but one- handed and pretty much blind to boot, given the location. i can slip in a screwdriver and push in the thingie that holds it together, but that's not enough. i thought of w-d or liquid wrench and letting it soak for a bit, but before i get under there and try that (which i can't do till the weekend anyway) i'm fishing for other brilliant ideas. i just don't want to crack and have to replace the other half.
ideas? thanks in advance.
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Couldn't you just cut the wires to the sensor and use a universal sensor? They come with a few inches of wire so you can just splice them to your existing wires.
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