The general disassembly of the lower is very much the same as the m4.
http://wem4guide.wikidot.com/lower-receiver-takedown
Start at step 5 for getting the pdw trigger group out
In step 9, when you pull the mech straight up and out...be careful of the spring and knocker cut off on the right side (not shown in the pic). The cutoff is referred to as part#66 for the m4. It will tend to pop out and the spring will really fly out. When you're taking the mech out, put your finger over it as soon as you see it. Then once it's out, take the spring and cutoff out for safe keeping.
Lots of other good stuff there too