Well, I think I found the cause of the fuel smell and fixed it.
I first used a vacuum gun connected to the tubing; there was a slow vacuum leak.
I removed and tested just the tubing, and it didn't leak.
I removed and tested just the solenoid, and it didn't leak. The solenoid is closed when not energized. The coil measured 27 Ohms, but I didn't bother energizing it because a stuck solenoid wouldn't have caused a fuel smell.
I removed the solenoid and saw dirt around the o-ring but the o-ring was in good condition, so I cleaned the orifice and the o-ring and reattached the solenoid to the canister and then reattached the tubing to the solenoid, and there was no longer a leak, but the real problem could simply have been that the solenoid wasn't pushed all the way into the canister in the first place. Drove it on a couple of errands and no longer smelled fuel. Hopefully, there aren't any other problems. By the way, I was surprised to see that there wasn't an external filter on the bottom of the canister, as I've seen on other older GM cars.

Glad you found the problem. We were all kinda sure that it had something to do with a vacuum leak, just from our own experiences. Do you know what could have caused the solenoid to not be pushed all the way in? Did you do work in that area recently? Just curious.

Also, re: the cannister. I also noticed that these new ones are completely sealed (at least my '97 is) if they go bad, you buy a new one...non-serviceable.

Nope, I didn't work in that area, and I mentioned the position of the solenoid because when I removed the canister while the solenoid was still connected, I saw that the body of the solenoid wasn't perpendicular to the canister; it was raised up a little.

I guess I would keep an eye on that for a little while, as the cannister can become clogged and stop working. It'* a failure mode, but I dont' know if it could cause the solenoid to back out or not.

Re the cannister: could a dirty filter in a cannister that has one be a cause of fuel smell?