Not sure you're serious on 2 fronts as it is quite easy.
Firstly, to change;
Try - settings, sounds then select ringtone and you'll see a list of ring tones.
Secondly, I would have thought a ring tone along the following lines would be more appropriate:-
(Feel a new thread coming on here)
Suggested ring tones for Consultants
I promised you a miracle - Simple Minds (or Junior ACN consultant)
Nobody Does It Better - McK
Hot in the City - Financial Services geeky consultant
Born Free - if you're a freelancer
Money Money Money if you've done your sales target
and Finally Ganstas Paradise - now who could this be ?