The COUPLER is $30, but the other materials run you closer to double that to do the job right.
You need to remove the SC from the car to do it. You'll have to 'double-nut' or jam nut the stud going through the Alternator bracket to get it out. The only tricky part of the job.
You need a new SC outlet gasket, two yellow coolant bypass o-rings that go between the SC and LIM, a tube of red GM gasket maker, ONE bottle of SC oil, although I suggest you get two now to have one on hand later, and I also suggest you get a fuel injector O-ring kit while you're at it, since you'll have all of them out at the time. You should also take the opportunity to clean the Throttle body, so get a new gasket for that, too.
Should take a first-timer with home-wrenching experience under their belt about 4-6 hours. It'* also a fun job that you won't regret tackling.
If you do all of the above, you're looking at 60-80 bucks. $30 will only get the coupler, and it'* not a very good paperweight by itself.