Midwest Industries makes a 12" and a 15" Mlock free floating hand guard that fit the M&P 10. I installed the 12" model, and I really like it. What you need is a DPMS-type low profile style hand guard. An Armalite-type, or a DPMS-type high profile style will not fit. There are other companies, such as UTG (their hand guards are made in the USA), as well. I am absolutely satisfied with my Midwest Industries.
In regards to scopes, there are many more choices. So many, in fact, it made my head spin. After much thought, I decided on the IOR Valdada 4-28x50 Recon. Here is what I like about this scope: variable power from 4x (close range) to 28x (long range, comfortably out to 600 yards and more). The 50mm objective lets in plenty of light. The scope is constructed with a 40mm tube (massive, rigid, and lots of range adjustability). It is a first, or front, focal plane (FFP), a feature that makes selecting holdover quick and easy. Parallax and diopter adjustments. The mechanical tracking of the turrets (imho the most critical criteria for a variable power scope) is 100% accurate, with mil adjustments matching the mil reticle. The glass is as good as it gets. IORs are known for their ruggedness. Good eye-relief. Overall length is 14", meaning it fits well on an AR. Here is a link to a youtube review:
For a fair price on this scope, check out SWFA. You can also find most competing scopes on their website, including the SWFA SuperSnipers (single and variable power).