Mrs. Officer

Tha Carter III Lil Wayne
Lil Wayne is using the term "head" here to mean oral sex and, as someone who has acquired their proverbial doctorate in head, he is asking to perform surgery, a.k.a. oral sex, on him.
Doing 100mph in a recently purchased convertible.
driving 100 miles per hour (a buck, since there are 100 pennies in a dollar) in a convertible (which has a convertible or "drop" top)
Lil Wayne is suggestting that his penis and the use of it on a female can resemble a police officer abusing someone with his/her baton.