Scott Hendersons Jazz Rock instructional would be a start. Its sorta the bridge between the heavy metal styles your used to, and jazz.
What I personally did as a kid was study Django Reinhardt, Birelli Lagrene, Joe Pass,
Frank Gambale,
Brett Garsed and basic sheet music.
If I were to do it again, I would do the following steps:
1) Learn the fretboard (All the notes on all strings)
2) Learn all inversions of all jazz chords
3) Learn all modes and how to correctly phrase them to get the emotional emphasis that makes up each different mode
4) Apply all above knowledge to basic jazz sheet music with "open for solos" segments, and playing with a track up until that point then trying to play a jazzy solo (smoothly changing keys and playing intervals, scale runs, correct phrasing to fit the song)
5) Then I'd get to progressively harder and quicker key changing music, with more complex chordal changes.
Jazz players also buildup lick libraries: Often taking licks and learning them in all positions, keys etc. and how they are most properly integrated into a solo. When improvising I'll often flow between licks whilst adding into scalar or intervalic filler or runs up to another lick.
