I ride mostly SS but put the gears back on if I'm going to a place with long draggy ascents, like the lakes or the peak. It takes me about 90 mins to put them back (rear mech never needs re-indexing as the cable just goes through the slots) front mech too, as i have marked the exact position where it goes.
I always put a granny on as well and keep all the bits (2 chainrings & bolts, chain, mechs & cables, cassette, chainstay protector, spare 9-spd powerlinks) in its own bag in the garage.
But recently I've gone dinglespeed for a road gear to get me to the trails. 34 and 36 on the front, 18 and 16 on the back and takes 30 secs to change. Magic ratio on a Soul with vert dropouts.
If it's steep enough to need gears, you'll probably need a chain guide, but there's nothing wrong in using your old front mech as a guide.