I just did this on my 97 s10 4x4. It took about 6 hrs including the drain/refill of the coolant.
I did use the felpro set; decent stuff and has been fine for about 2000 miles so far.
Remove all the heater hose connections to the lower intake,
remove all of the sensor wires and move them aside. I like to mark each one with numbered tape or colored tape; however, they are each unique so you could skip that step. De-pressurize the fuel system and disconnect the lines near the firewall. You DO NOT have to remove the upper intake from the lower to remove the unit.
Unbolt the lower intake and remove carefully. Clean all the gasket surfaces (make sure you cover the lifter valley while doing this so that gasket crap doesnt fall into the crankcase. Assemble the gaskets to the heads, put black RTV on the front and rear block lips then install the manifold assy. Use thread sealer on the bolts. Torque to spec and reconnect all of the hoses/lines/wires in reverse order.
I would and did change the oil as mine was leaking internally and I wanted to make sure that no small particles were left behind.
Refill with coolant and test drive. Good luck if you havent already done this.