You imply you have a model, albeit conceptual. Can you describe it?
In its simplest form, sensitivity analysis, in the gis sense of the term, could involve varying a variable/term in the model within a range to assess the change in outcomes. For instance, you model may have a factor 'X' which according to the literature is supposed to have an impact on 'Y'. You may find that varying the range that 'X' has within the model, you can view the change in 'Y' to see if this is correct. Quantitative models are best suited to this sort of analysis because simple cases of X affects Y don't look at the combined impact of other variables, some which may mitigate X's affect on Y.
So what do you have?
What is the form of the data? (raster, vector, a combination)
Software availability and version?
Familiarity with other non-gis software?
Familiarity with statistics? (both spatial and inferential)
anything else you can add