I suggest you use the System Usability Scale.
This is a 10-question, Likert-scale survey used to measure respondents' assessment of the usability of any system.
The survey does not explicitly ask about "information overload", but its questions address related concepts:
On a scale of 1 to 5, where 1 = strongly agree and 5 = strongly disagree
- I think that I would like to use this system frequently.
- I found the system unnecessarily complex.
- I thought the system was easy to use.
- I think that I would need the support of a technical person to be able to use this system.
- I found the various functions in this system were well integrated.
- I thought there was too much inconsistency in this system.
- I would imagine that most people would learn to use this system very quickly.
- I found the system very cumbersome to use.
- I felt very confident using the system.
- I needed to learn a lot of things before I could get going with this system.
The aim of the survey is to produce a single score -- a benchmark -- that can be compared with scores produced by other other users of the same system, or of other systems.