Anyways, if I want to change たべる into ~たら form, do I make it たべたら or 食べるんだったら\食べるのだったら\食べるのであれば, like my lang-8 friend says?

Waiting to hear what you guys/gals think.

While it’s probably a colloquial thing, I didn’t think you could have a copula「です・だ」after a verb. I’m most likely wrong, if it’s what your lang-8 friend is telling you. But「食べたら」is correct in the most basic sense, like 「すしを食べたら・・・」. Have you read the TextFugu lesson on たら form yet?

:)

You can put the copula after verbs in an explanatory tone.
Plain form + の/ん + copula

I’m no native, so take this worth a grain of salt, but this construction used with a conditional gives me the feeling of a hypothetical or counter-factual statement.

Like: If I were a bear, I’d build a spaceship of fish heads and sail the stars for eternity.

What was the context of your original sentence, just out of curiosity?

And yeah, the “hypothetical” statement idea seems to make sense, to me anyway.

僕は熊になるんだったら、いつまでも星の中で、魚の頭で作った宇宙船で飛びます。

@Kyle:
Here’s my original sentence:
寿司をたべたら高い寿司を食べくない
(What I meant to say was:’If I’m eating sushi, I don’t want to eat the expensive ones’.)

And here’s the correction by my friend:
寿司をたべるんだったら高い寿司を食べたくない。

When I asked her/him about it, she/he gave this reply:

食べるんだったら＝食べるのだったら＝食べるのであれば
“I don’t want to eat the expensive sushi if I eat sushi.”

Still a tad confused, but glad to know that 食べたら is fine too.

Also, I think the correction given was more focused on the 食べたくない vs 食べくない.