Personally I think asking a theoretical question this way causes the customer to guess, which is rarely a good idea. Asking them something like: "In the past when you have an encountered a defective product, how likely were you to buy it again" would be more concrete.
I am not sure how you would do this with descriptive statistics. If your answers are from 0 to 100 percent (that is future purchase levels your dependent variable) then you can do this with linear regression which is the simplest regression. It allows you to put all the factors that contribute to future purchases in the model at once so you can see which is relatively more important and control for the other. But you have to understand regression to do this and you can not check for violations of the assumptions in excel to the best of my memory. Its dangerous to do regression without checking assumptions. You could run the results in SPSS which does have the diagnostics and then (maybe) find a way to transfer them to excel. In honesty I stay away from any statistics in excel, I use it only as a reporting tool.
You can do a chi square test to determine if one of the variables you mentioned appears to influence purchasing, but you have to do that one variable against purchasing at a time (not all of them against it at once). That is the simplest statistic I know of and requires few assumptions.