Handguard replacement is simple, but it may take two people. See the ring between the handguards and the receivers? That's what holds the handguards on, and it's under spring tension. Stand the rifle on its butt, and pull down on the ring. Have someone else pull the handguard halves off.
Most replacement handguards will have a top and bottom half instead of the left and right of these old triangle type. Virtually any rifle-length handguards will work with no modification. The only exception I can think of would be the "Sudanese" style AR10 handguards that Armalite made, as those require a round handguard cap. Anyway, you wouldn't use those anyway.
[url]www.adreanalinearms.com[/url] sells Cavalry Arms furnature, so if you want to install some A2 handguards, that's the place to go.
The stock is slightly more involved, but unless you get a carbine-length upper, I'd leave the stock as-is. You're already starting out with an A1-length stock, which is ideal for most folks, and much better than the longer A2 stock, which fits only large, monkey-armed folks. [:D]
-Troy