I got used to being the uke and getting my wrist bent in unusual and painful positions, and then took my turn at being the nage. I was afraid that I was going to screw up horribly and accidentally hurt someone, but the students there have done these techniques so often that their flexibility is incredible. One woman ,as I bent her wrist into what I thought was a pretty uncomfortable position, was like, "No, no, more. More. More… okay there," until her wrist was almost pointing toward her elbow.
Anyway, I was eventually put into all sorts of interesting positions that my body was not used to (arm behind my back, shoulder being pushed in a direction that would be disabling if someone went full force) and got a few lessons in pain from the Sensei. However painful it was to be on the receiving end of some of the techniques was, I was never in pain for more than a short moment; just enough to get the message across that these techniques were effective in getting an attacker to stop without actually doing permanent damage. It wasn't so much pain as it was intense discomfort.
I'll probably be back in class on Monday and I hope to go to the dojo at least twice a week, which will also add toward another goal of mine. I don't think you can ever completely "learn Aikido," as I think it is definitely a life-long process, but I'll keep making an occasional update of my progress on my blog and maybe check this goal off when I feel confident about what I've learned.