Please explain the down vote so that I can update the question to eliminate the problem.

Further, I understand that I shouldn't buy individual modifications, but I would still like to know which mods I should be focusing on. I'll update my question to clarify this.

Perhaps I should have been more clear in my question. I am not intending to act as a full-blown Tank in Operations and/or Flashpoints via Group Finder or otherwise. I want to have gear that would allow me to take a lot of hits in, for example, H2 mission and Planetary Stories while grouping with my two Glass cannon friends (Gunslinger and Shadow). I'll update my question.

@Vahx Ah, yes, I could do that, that's true, but since the information came from Nando, I'd prefer it if they were the one to get the, no pun intended, credit for the answer.

@Vahx Yeah, I figured that's where the vendor would be. Yes, but the profit you state is not exact and, I'm guessing, neither is his: exactly 4400 credits seems an unsually exact number, especially considering the 48 extra credits from the armoring. As such, I don't feel comfortable accepting his answer.

@Nando Could you update the answer to include more information on where to find the vendor and the exact amount you net from each purchase/sale?

So, is the 4.4k including the 48 credits you get from removing and selling the Armoring?

What's the cost of removing the Armoring from the Shield, and is that already subtracted from the 4.4k?

@Vahx Yeah, I've seen that option floating around various forums and such. Since prices on GTN may fluctuate a lot from one day to another, I figured vendoring would be a safer bet and, since it is less prone to change (would require a patch change from BW), more suited for this Stack Exchange. But thank you for the tip, I might try it out. :)