I would wait til it was between 7-10 days before even bothering...the beer is fermenting fine, so there's no point in openning it..You only now need to know when the beeer is finished if you decide to secondary (and I usually don;t do that til the 14th day anyway)
Here's what I do....
1) With a spray bottle filled with starsan I spray the lid of my bucket, or the mouth of the carboy, including the bung. Then I spray my turkey baster inside and out with sanitizer.
2) remove lid
3) Draw Sample
4) fill sample jar (usualy 2-3 turky baster draws
5)Spray bung or lid with sanitizer again
6) Close lid or bung
7) drop hydrometer in sample jar and take reading
It is less than 30 seconds from the time the lid is removed until it is closed again.
Probably less if you have help.
It's easy peasy!!!