This verse has the feeling of being a common folk saying, which perhaps it was. It is a play on words, describing both vultures around a corpse and omens around times of trouble. This version has a word added and another subtracted to make it look more like Matthew 24:28, which this is clearly a version. It is not clear if this verse is positive or negative.

The "wheresoever" is from a word that means "somewhere", "anywhere", "wherever," and "where."

The word translated as "the body" means "body", either living or dead, but it also means anything physical or solid. Like our word "body" it has special meanings such as "body" of proof and the "body" of a document. It is the opposite of "spirit" but more connected to the "soul" because it is part of this life. See this article about Jesus's use of words related to a human being. The word is different than the "carcass" used in Matthew.

There is no verb "is" in this verse. There is in Matthew. 

"Thither " is a word meaning "there", "in that place," and in philosophy means "the intelligible world."

Eagles" is from the Greek word for "eagle", "bird of omen", or "omen." It is a Greek word, but this word was used in the Septuagint to translate the Hebrew word for "eagle" (nesher), which means both "eagle" and "vulture". Among the Jews, it was forbidden to eat eagles, along with buzzards and vultures, so they were grouped among carrion birds. Some uses of this word, such as Micah 1:16, which refers to the baldness of eagles, clearly referring to vultures, which are bald. (Bald eagles, of course, are not bald but have white feathers on their adult heads and were not known in the ancient world.) While there are positive characteristics of eagles in Jewish writing, based on their size and strength. This view of eagles in the West is positive, but this comes from Greek and Roman culture, which had a very positive view of the bird, but they also saw eagles as a bird of omen.

"Will be gathered together" is from a verb that means, literally, "collect and bring in". This less command and an extended version of the verb translated in the same way. In Matthew 24:31 Jesus uses this verb to refer specifically to the gathering of the elect.