Another advantage to removing the engine is you can replace the shitty plastic oil separator plate and inspect the rear main seal.
It's also way easier to torque the heads on properly. The procedure involves torquing the head bolts in a specific pattern, backing them off, torquing them down again, and then cranking the bolts 180 degrees which is easy to visualize with the motor out. I may have the sequence off so don't quote me on the order, lol. The 180 degrees bit can be accomplished with the engine in the bay if you have a degree wheel thingy.
Also, when the engine is out on a stand replacing the timing belt, water pump, plugs & wires, scrubbing the engine all sparkly clean, cam seals, crank seal, sealing the oil pump, etc. is a snap.
I posted the FSM head gasket replacement procedure here: http://legacygt.com/forums/showthrea...ti-186097.html
. It's for a first gen 2.2 but it is the same for second gens more or less.