Ando,
to fix the problem you do NOT need to open the side that says not to open.....seriously if you do ever have to open the side that says do not open do it for curiousity once the retractor is truely dead.......
I once opened the side that says do not open & I speak from experience
.....It took me SEVERAL hours trying to manually rewind the spring that WILL come out in a big hurry if you ignore that warning.....
But for the other side there are no surprises - just be carefull not to lose bits....seriously it's a very easy clean/fix....