The Monogram and Airfix Saturn V kits are different kits. From an accuracy standpoint, the Airfix is the preferable kit, and $10 is not a bad price at all. The Airfix kit has much better engine detail; the depiction of the J-2s on the Monogram kit's second stage would be a fairly funny joke were they not serious. (If you've seen it, you know what I'm talking about.)
Whichever kit you go with, though, you need to work on the Apollo spacecraft, basically everything from the LM adaptor on up. Both kits feature Service Modules that are proportionally too tall and aren't Block II versions. The BPCs have no detail to speak of.
But for $10, you'll have dough left for the aftermarket stuff....