These are not very common, but I've just looked on the Guns America website and found classified ads of this magazine type for sale. Gun Broker and Auction Arms could likely yield similar findings. I'm posting related links for all three sites, but you will have to enter the search terms yourself, which I am doing to ensure there is no conflict of interest or violation of policy pertaining to links by referring you to a specific vendor on these websites.
100-300 USD or so
Up to 200 USD
$100-$150, depending on exact model and condition.
No published sn data.
Llama has a tradition for not being a particularly high quality manufacturer. While they're not the worst on the market, there's a number of pistols you can purchase for around the same price which are superior.
AFAIK, there is no published data on Llama serial numbers.
A llama 22 magazine can typically be found at gun stores, shooting ranges, or online retailers that specialize in firearms accessories. Make sure to check the compatibility of the magazine with your specific model of llama 22 before purchasing.
100-300 USD
Best left to a gunsmith
No published sn data.
50-150 USD
50-175 USD or so