Can someone tell me if the factory handguard will accept a foregrip or if I would need a rail piece to attach an angle grip. From the pics I've seen it looks like it would take an M-Lok attachment.

You will probably have to install a piece of rail, and the skinny handguards on the MP 10 may or may not give you issues with that.

Otherwise you can switch out the handguard for a model with rails. However, be aware that the MP10 has a proprietary design and some diligent research will be necessary to find a compatible handguard. The MP10 is not as plug and play compatible as the MP15 models.