If the gums are red that may signify gingivitis (low grade gum infection), the smell could signify a more advanced infection. AFAIK oral health is pretty much the same in humans as in animals - teeth and gums are composed of the same basic materials, and they as susceptible to plaque, tartar and cavities just as we are. Please note I do not purport to be a dental expert nor a kitten authority!
A recent thread discussed natural alternatives to a full dental, tho as there is a smell I'd be inclined to get it checked by the vet as you wouldn't necessarily see or feel an infection if it was deep-seated. If you do need antibiotics be sure to purchase some probiotics (beneficial bacteria) such as LactoB, as the ABs will wipe out the good guys as well as the bad guys.
http://www.purrsinourhearts.co.uk/index.php/topic,35102.0.htmlMight also be worth checking your pet insurance policy - most don't cover routine dental work, but given this is a young cat you might be able to argue this is not routine. I don't know how these things work as never had to claim on Noah's policy, but it can't harm to try!