well it depends, if you want to go SS, it's easy, if you want to go Fixed, it'd be a little more money spent. both are simpler. provided you want to go SS, you just buy a SS kit like Gusset, and a chain tensioner, then you strip your derailers, shifters, extra chainrings, and cassette and whip it up, and that's if you do it RIGHT. the thing i love about SS is that there is much less to break, so it's up to you

to go fixed, a new rear wheel is needed, and you either have to find a "magic ratio" or get an eccentric rear hub.