Just go ahead and do it Miguel... There is not a lot to it... It is pretty simple.
There are 2 screws that clamp the twistgrip to the bars... take them out and split the housing and you will see where the cable fits into the plastic throttle tube... slip it out... and now you can inspect everything.
Two stroke oil will be fine... don't use too much...smear it on with a finger.... (but clean it all first)
Examine the cable and slide it in and out to see if that is where the resistance is.
The resistance is usually one of 3 spots.... the twistgrip, the cable, or the carb slide.
And just be careful putting it together and don't force anything... and if you have to do it 4 times before it is right.... No big deal.