99 Plymouth Neon with possible shock or strut issues...?

The only true way to tell is to check is while on level ground bounce both sides of the car buy pushing down on it and see how it goes down and back or look at the offending wheel strut and look for leaks other wise take it to a shop the measurement you done does say there is an issue in the suspension system but does not indicate any thing for sure. could be lower support arm bushings or upper or a lot of other things. As for cost if struts or shocks figure 100.00 and axle just for parts labor will be a differant issue.