Its not bad, Pop the bearing in the top half of the connecting rod. You'll need to put some rubber hose or you can buy the actual protectors to go around the connecting rod bolts. Point the notch in the top of the piston towards the front of the engine. Then with the covers on, slide the piston/rod assembly down as far as you can go, usually the piston rings will stop you. Then put your ring compressor on the rings gently tap with the handle of the hammer the piston in, until the connecting rod is about a 1/4" from the crankshaft journal. I like to turn the crankshaft until it touches the bearing. Pull your covers off your rod bolts. Then I put the other half of the bearing the in the cap side. I put the cap on, and draw up the bolts, then I torque the nuts down.
You'll want to oil all parts as you put them in. I recommend Melling's assembly lube. I may have let out a few details, but you'll be able to figure it out.
1989 Firebird L03
1993 Thunderbird 5.0 HO
1995 F150
Gonna be building a 351 Boss this summer!
Summer's over, never got to it...
This is my current build though
http://www.302w.com/Forums/forums/thread/1100.aspx