well anyway i have spearhead and the multiplayer is awesome. The new maps are massive, you can actually get lost. I havnt yet played single player but as soon as i do i will let you know my opinions on it.
YES, you need Medal of Honor : Allied Assult to play Spearhead. Spearhead is an expansion pack for MOH:AA. The newest patch for MOH:AA is included on the Spearheard CD so you wont have to download the newest patch, this patch is nessesary to play Spearhead. Once you install the newest patch your saved single player games will NOT work for the Allied Assult Game