Go to Home Depot and rent a steam cleaner for about $30/day and do the interior yourself.
As for the engine, go to crappy tire, buy a can of engine shampoo and follow the directions on the can :p j/k...It's easy;
-work on a cold engine
-cover electrical components (alternator, battery, harness' (optional) ) using a shopping bag or whatever
-apply engine shampoo generously
-let it sit for a few minutes
-scrub stubborn stains with an old toothbrush/wire brush
-rinse with water well
-repeat if necessary
Tada!