Is eating rice well after its use-by date a bad idea?
Rice is one of those dry staples that last a looooong time if stored properly, which in this case means cool and dry and safe from insects.

The more critical part is the seasoning. Ground spices tend to loose aroma quickly. This does not mean they will necessarily turn bad, but possibly a bit bland. Mold is only a problem when humidity comes into the equation, like with the rice.

Even more critical is fats. Some spice mixes contain fats, they can go rancid after a while. I suggest you check the label. 

So:


check the rice for "critters" and their traces
sniff at your seaoning mix in case something smells off


And if everything seems ok, enjoy your paella.



Edit as your question focuses on the rice:

White rice stays safe "indefinetively", brown rice has a limited shelf life of a few months as its fats can turn rancid. See Still Tasty for more.

In the unlikely case that your rice is off (or for future paella dishes), use the so-called bomba or Calasparra rice. A Spanish short grain rice with a lower starch content than the Arborio used for a ceamy risotto.

For substitutes, sources are at odds: 


some say use arborio for the most similar grains, but you'll get more sticky results
others favour long grain rices because the rice is less sticky.