I'm assuming you mean either a 1993 Toyota Camry or 1993 Lexus ES300 with the 3.0L V6? There is no Camry ES300 model that I know of - at least in the North American market.
Anyway - the engine is shared between them, a 3VZ-FE V6. A fairly commong engine so parts and info should be relatively easy to find. As being serviceable - depends on what happened to it. The engine is a 60 degree cast iron block with aluminum heads - the bottome end (block, crank) is usually pretty bulletproof - the heads you will have to check for warping (if replacing the headgasket - otherwise you might be just wasting your time).
If I am thinking of the correct allen head bolts - then they will have to come off, but there should be more than two of them. I would recommend getting the right tool for them as well as a torque wrench, if you don't already have them. Keep in mind that most of those bolts on the head are NOT reuseable - they were designed to stretch when torqued down correctly. Be a pain if you did all that work and had to break it back down for a broken stud.
2002 Corolla S, Silverstream, 1.8L 1ZZ-FE (VVT-i)
2003 Matrix XRS, Cosmic Blue, 1.8L 2ZZ-GE (VVTL-i) - RIP
2009 Matrix XRS, Blue Streak, 2.4L 2AZ-FE (VVT-i)
