PC Upgrade and FFXIV Settings Questions

[Noob]

Before I start, my apologies for such a long post. I have been messing with the graphic's cards settings, trying to get the game to run smoothly. In order to have a somewhat smooth FPS, I need to have the settings on both my graphic's cards and FFXIV's configuration screen all the way down as well as playing the game in the lowest possible windowed resolution. I understand my graphics card is outdated for FFXIV (recommended graphics card being a GTX 450). With that said, I'll begin by listing my PC's specs and getting to my questions on how upgradeable my PC is.

In December of last year, my parents bought me a Dell XPS 8000 Studio. It came with on board specs. The system specs are the following:

Intel Quad Core i5 CPU 750 @2.67 GHz
6GB RAM (After installing FFXIV, I have 3.5GB remaining RAM. Planning to upgrade to the maximum of 8GB.)
Nvidia GeForce GTS 240 Graphics Card
I'm not sure about my PSU. I'm guessing it's a 350W PSU since that came standard at the time mine was bought.

I've searched all over the internet, trying to find out how upgradeable my system is without any luck. Here are my questions:

1.) Would I be able to run FFXIV on max settings with my CPU only being 2.67Ghz?
2.) Would I need to upgrade from an i5 750 to an i7 950+ to play FFXIV on the highest settings with no lag (bar AO and DoF)?
3.) Would anyone know whether or not my PC has the needed slots to handle either of the two best graphics cards (GTX 480 or the ATI 5870)?
4.) Which of these 2 cards will better run FFXIV?
5.) If I remove my PSU to check the sticker, seeing what wattage I have, could any bad come from this?
6.) If my PSU is indeed 350W like I'm speculating, would anyone know if my PC's PSU is upgradeable to a 500W+ or is it one of those models which cannot be upgraded past what comes on board (I've read online these cards require a 500W+ PSU to handle them effectively)?
7.) Is overclocking your CPU necessary to play FFXIV on the highest settings with no lag (bar AO and DoF)?

I apologize for so many questions. I've just started learning about what's involved with gaming PCs this week so all of this is very new to me. I'd greatly appreciate any info anyone can provide me. I'd like to make whatever upgrades necessary (if it's possible with my PC) to play FFXIV at the highest settings.

[sruon]

1) Doubt it
2) No, i5 750 4.2 Ghz GTX470 60 fps everywhere, down to 45 near aetherytes with Antialiasing x8 and everything high
3) Yeah, probably
4) I'd say the 480 but technically... same deal
5) Dell? Probably lol.

[Noob]

Thanks. Are you overclocking to reach 4.2Ghz on an i5 750?