I have created a short version of the NASA TLX questionnaire without weighting) step based on the code provided by Keith Vertanen. The extended version is recommend if you have the time to conduct it. In many papers in the mobile HCI, Augmented Reality and Virtual Reality it is practice to use the non-weighted version. Decide on your own which version to use.
You can find versions of the short questionnaire here:
Excursions into Augmented Reality and Mobile HCI 