InfoPath Dev

Hi planning a infopath 2010 "change" form where a End user is found by the people picker and then +10 fields get's populate with the info on that user. (name, manager, address, phone, department etc. etc.) The user who fills the form, then changes one or maybe 2 fields (maybe more) and hit a submit button which then should put the changed data back to AD by a SP workflow But how can I "capture" the one (or all fields) that have changed?

One quick & dirty codeless way is to associate a TRUE/FALSE Boolean field with each information field.  If you only have around 10 information fields, it shouldn't take that much time to add these and set their default values to FALSE.  Then, add an action rule to each information field that will set the associated Boolean field to TRUE.  This rule will only run when the information field is changed...which is exactly the event you want to capture!