hmm... What i'd do is strip the interior, all the seats etc, have them steam cleaned. Put the carpets in the wash, use fabric conditioner on them to dispose of the smell and give them a nice feel. Remove the A/C vents, plug em up with old socks or something and let off a bug-bomb. Then vacuum up the remains, wash the windows, wipe down the dash and trims etc, and youre set.
Thats assuming the little buggers arent in the actual ducting and in the doors..
PS while the carpets are in the wash, it might be an opportunity to install some noise deadening materials in the footwells..