How should this painting's title, signature and yin (chop) be correctly translated?
The title is 海棠珍禽 - Begonia and rare bird. It's one of the common themes for classical Chinese painting, which I believe is what this title is for.

The first two characters are Malus spectabilis, however, when Chinese say 海棠 especially in art works, we actually mean 秋海棠 - Begonia grandis, which is an herb instead of a tree. 

The last two characters are literally 'rare bird'. They are sometimes extended to refer to any rare animal, but in the context of a painting it is referring to a bird.

The signature looks like 子兰作 to me, meaning the Zi or Hao of the artist is 子兰. (If you're not sure what Zi or Hao is, think Zi as a secondary given name and Hao as a stage name.)

Can't see the seal clear enough, best guess is 吴兰之印, indicating the full name of the artist is either 吴兰 or 吴兰之. Since we know the artist's Zi is 子兰, the name ending with 兰 (i.e. 吴兰) is actually more likely than the other.