The North Face’s Condor, which was sold during the late 1990s for about $350, sure looks to me like it was meant as a four-season tent, so I’m a little puzzled when you say you’ve learned otherwise. In its original configuration the Condor was a beefier version of the three-season Peregrine, meaning mainly that it had less mesh in the canopy.
In any event, I simply can’t believe it won’t be adequate for your North Cascades trip in June. True, the weather is apt to be atrocious. Sorry, but although it’s 75 degrees and sunny in Seattle as I write this, June is a notoriously non-summer-like month in these parts. Summer starts July 5, like clockwork. But, either way, it shouldn’t be really cold. Even if you climb Mount Baker you won’t be camping much above 7,000 feet, so even a three-season tent would be perfectly adequate. And just about any tent is sufficiently rainproof for your purposes.
I don’t doubt that TNF can provide a copy of the Condor’s instructions, although if you have setup figured out, they won’t add much. Call the Warranty Department at (800) 447-2333.
Take some time now to get the tent out, set it up, and make sure it’s all in good working order. Let it air out thoroughly as it’s possible it might have a touch of mildew. If severe, then that’s another issue. Make sure all the poles are in good shape, there are no big nicks, the elastic snaps them back into place. If you have skinny wire-style stakes, get some snow stakes聴they’re wider for better grip in snow. And get some four-mil plastic sheeting at the hardware store and cut a ground cloth that’s a little smaller than the footprint of the tent.