My 5 year old daughter complains of pains (leg, knee, stomach, foot, . ..) and also complains of exhaustion. Potential course of action?

Get a thorough exam. By her pediatrician to verify her heath status and make sure there's nothing physically wrong. If everything checks out ok, consider that there could be a reason she's complaining other than leg, foot, stomach pains and exhaustion. Something could be "stressing her out".
Rule out Lymes. I would contact your dr. For an evaluation.
More detail needed. Although there may be simple answers, such as too much activity, not enough sleep etc, best course is to consult with your peditrician to revies the details and do a good physical exam.