This right?

[Grangy]

I'm new to the language and wondering if this is even remotely close to what I meant:

Oe Plltxe Lu Stawm.

Intending to pretty much be "I say what is heard".

[omängum fra'uti]

A few things.  The first is that the "be" in there (is) is an English thing.  It's a helper for "hear" to make up for the lack of verbal inflections English has.  It's not needed in Na'vi.

What is needed, though, is something to indicate that is what you are saying, and that it is what is heard.  Lets look at the parts.

Oe plltxe - I speak
Oel fì'ut plltxe - I speak/say this

Now we have that you are saying something specific.  But not what that is.  For the second part...

Stawm - (I) hear
Tsat stawm - (I) hear it/that
Tsat fkol stawm - That/it is heard (One hears that/it)

Now to put the two together, we use "a".  I'm also moving the words in the first part to make it clearer.

Oel plltxe fì'ut a tsat fkol stawm - I say what is heard

Now you can shorten that a little bit.  For one, fì'ut a can be abbreviated futa, and the "tsat" probably can be left off and understood as being there.  In which case, the final phrase would be...

Oel plltxe futa fkol stawm

[Grangy]

A few things.  The first is that the "be" in there (is) is an English thing.  It's a helper for "hear" to make up for the lack of verbal inflections English has.  It's not needed in Na'vi.

What is needed, though, is something to indicate that is what you are saying, and that it is what is heard.  Lets look at the parts.

Oe plltxe - I speak
Oel fì'ut plltxe - I speak/say this

Now we have that you are saying something specific.  But not what that is.  For the second part...

Stawm - (I) hear
Tsat stawm - (I) hear it/that
Tsat fkol stawm - That/it is heard (One hears that/it)

Now to put the two together, we use "a".  I'm also moving the words in the first part to make it clearer.

Oel plltxe fì'ut a tsat fkol stawm - I say what is heard

Now you can shorten that a little bit.  For one, fì'ut a can be abbreviated futa, and the "tsat" probably can be left off and understood as being there.  In which case, the final phrase would be...

Oel plltxe futa fkol stawm

Irayo, I spent some time looking over the dictionary and several documents/worksheets/just about anything I could find on Grammar (My worst point in just about every language). Most of the stuff effectively melted my brain, partly due to my unfamiliarity with terms such as "Verbal Inflections", "Ergative", "Accusative", to name a few among many associated with learning Na'vi. The vocabulary isnt TOO hard, since I'm used to studying translations of vocab, though.

[kewnya txamew'itan]

I'd go a bit simpler than omängum with this,

I'd go with:

Oe-l f-ay+u-t(i) a-stawnawm plltxe

the f-ay- is a contraction of fì-ay+ and means these, 'u being thing and becoming u due to lenition from the ay+.

stawnawm is the passive participle of stawm and effectively compresses the entire clause "a fko stawm" into one adjective.

Alternatively, going even simpler (and possibly more correctly because to me using plltxe transitively sounds a bit strange):

Oe plltxe nìstawnawm

or with a more reasonable translation, I speak in the manner one hears. Here the nì makes the adjective (stawnawm) an adverb.

[Hawnuyu atxen]

Oe-l f-ay+u-t(i) a-stawnawm plltxe
Alternatively, going even simpler (and possibly more correctly because to me using plltxe transitively sounds a bit strange)

If you using plltxe transitively, than do so

[kewnya txamew'itan]

Gah! Irayo ma Hawnuyu.