As long as you are using an AirPort base station, it should be plug and play. Once you have the SSD set up and running in your iMac, you should be able to plop the HD in the enclosure, erase it, then plug it into the AirPort and you're off to the races.
By the way, I did the exact same upgrades to a mid-2010 21.5" iMac: 120GB SSD and 4 more GB of RAM for a total of 8.
The SSD of course is great: for example, iTunes is open in one bounce of the Dock icon. What was surprising was that the increase in RAM, which I did about a week after the SSD, was fairly noticeable too, which surprised me.
Very satisfied with my iMac: planning to get at least three more years out of it.
Oh, and concerning TRIM support, I downloaded this free install:
http://www.downloadcrew.com/article/21037-trim_support_enabler