Maryland will have CCW reciprocity shortly after the revolution or the freezing of Hell.
As far as car transport, in a word, no.
You're headed to a destination in Maryland, so the federal peaceable journey law doesn't apply. Maryland does not permit you to keep a gun in the car - anywhere in the car - unless you are headed to / from a gun store, range, etc. And you can't make extraneous stops then.
The way I read this is that since you are going to a friend's house and not one of the listed facilities, you cannot lawfully transport the gun in your car in Maryland.the carrying of a handgun on the person or in a vehicle while the person is transporting the handgun to or from the place of legal purchase or sale, or to or from a bona fide repair shop, or between bona fide residences of the person, or between the bona fide residence and place of business of the person, if the business is operated and owned substantially by the person if each handgun is unloaded and carried in an enclosed case or an enclosed holster;
Section 4-203 - Maryland Criminal Law - Maryland Code :: Justia
I'm so glad I escaped that state :)