失礼します～ Comparing 2 sentences

[Isaboo]

みなさん、はじめまして～よろしくお願いします

I have been a subscriber for years but I have never posted in the forums. Wow!
I use Lang-8 as a way to practice Japanese reading and writing. I wrote an entry the other day, and I was corrected (naturally!), but this sentence in particular interested me.
Here is my flubbed up Japanese:
勤め先に、私が大きな企図を働いてる。

I was then corrected by 2 different people who gave me two pretty different corrections. The first one:
勤め先で、私は大きなプロジェクトに取り組んでいる。

And here is the second one:
勤め先で、私は大きな企画（きかく）のために働いています。


I fully understand the correction for 勤め先に　→　勤め先で, but I was wondering about the rest of it. Is it better to use the katakana "purojekuto" rather than 企画? Any help in understanding the two sentences better would be greatly appreciated

[jaboyak]

In my opinion, it is just a different way to say the same thing, for the most part. The first sentence is more of a "I'm taking on a big project at work" kind of feeling, whereas the second one is more of a "I'm at work because of a big project that I'm working on." kind of feeling.