Theres this pretty dope plugin, called Slayer2. It was/is be ReFX, and FLStudio comes with a very workable but stripped down version of this plugin. It emulates guitar cabinets and amps and comes with loads of little effect pedals that sound quite good (especially the rotary pedal) . Ive gotten pretty convincing results with the vst plugin. Havent messed with the FL one too much so wouldnt be sure on that one for ya. You can do some awesome distortion, and you can setup various strumming modes and delay times, as well as chords. You can do alot of convincing guitar parts with this plugin, it just takes a lot of work, and thats not because the plugin sucks, but because its very hard to emulate a guitar with synths or just plain samples. any real musical instruments creates very complex waveforms and harmonies, and have to take physical modeling, reverb, etc. in to account.
This means that you are going to have to put in a lot of work to get convincing results. you have to think like a guitar player and think of the guitar and hjow it works. set up your pitchbend to one or two semitone range up and down, and mildify your modulation. if you put in a lot of work like this you can even make convinving guitar parts with a crappy oem soundcard fm gm midi guitar patch.
Good luck
Peace