A good shop or mobile detailer thats actually knows what he/she is doing would charge aound $225 +/-. If a detailer says they can do the engine/exterior/interior for less then $200 I would bother with them. Chances are they are going to use products that have a crap load of fillers and just hide the imperfections instead of actually fixing them. If your just looking for exterior work then about $125.