The OEM2 lacks the delta assembly and front cap, so you can't just stick a Magpul hand guard on it. You'll need to either go with a free float that clamps to the standard barrel nut (like Tig recommended) or switch it out for one that uses its own barrel nut.
For the buttstock, I'm a fan of the simple Magpul MOE carbine stock. You can usually pick one up on the EE for around $25. And I'm one of the few that still uses the standard A2 pistol grip, but Magpul makes plenty of good grips. The standard Magpul BUIS will work just fine as well.
When you install the trigger guard, please make sure you support the receiver when installing the roll pin.