Josh, I'm gonna guess that you've figured out the answer already, but in case not, here goes.
You can figure out the 7 chords by taking the basic chords and adding a 7th according to what is available in the scale of the key you're working in. For instance, if we take the C major scale and start with the I chord, we have the C major triad. If we add the seventh, we use B natural (because that is the 7 available in the scale) and we get a major seventh chord. Moving on to the II chord, we have D minor. The 7th would be some variation of the note C. We know it must be C natural, because that is the C in the C major scale. This gives a D minor 7. For the III we add D natural to E min, also giving a minor 7 chord.
On the whole for the scale, you should be able to get:
Cmaj7, Dmi7, Emi7, Fmaj7, G7, Ami7, Bmi7b5, Cmaj
In general then you can say for any key that you have the pattern:
Imaj7, IImi7, IIImi7, IVmaj7, V7, VImi7, VIImi7b5 and Ima7
You can figure the same thing out for a minor key as well. It's the same pattern, but starts on the 6th scale degree of the corresponding major scale (i.e. Imi7, IImi7b5, IIImaj7 etc...)
One of the things about jazz is that songs tend to change keys a lot within the song. You can spot this by looking for dominant 7ths, since each key only has 1 possible dominant 7. If you want to see this in action, take a look at the first 2 lines of Autumn Leaves. The copy I'm looking at has the progession: Ami7, D7, Gmaj7, Cmaj7, F#mi7b5, B7, Emi. Look at the first V7. It is D7, which is the fifth scale degree of G major. Immediately after it is the chord Gmaj7. We are in the key of G major here. Also, before the D7 is Ami7, which is the second scale degree of G major. This is a classic II, V, I pattern.
The next time a 7 chord comes up, it's B7. This is the fifth of E, but after the B7 is an E minor chord, meaning that we're in E minor now. Before the B7 was F#mi7b5. This is the II chord of the E minor scale. This is a II, V, I progression in E minor.
Looking at the first 2 lines as a whole we have: II, V, I in the key of G major, a stray C maj7th Chord (which could be considered the 4th of G major) and then a II, V, I in the key of E minor.
Hope that makes some sense.