Upgrading GPU from Integrated GFX?

Let me start off by saying I am fairly new to the world of computer hardware. I tend to stick the the coding and not worry about whats under the hood so this might be a ridiculous thread but idk. Basically I'm wondering if its possible to upgrade from the crappy integrated graphics that came with my desktop to a nicer card once I have the funds to do so. Here are my embarrassingly pathetic specs.

CPU: Intel E5500 Dual Core @ 2.8GHz
GPU: Intel HD Integrated GFX
RAM: 6.0GB DDR3 DRAM Freq. 399.0 MHz
PSU: No Clue
MOBO: Gateway Model WG43M Intel Chipset G45/43
HDD: 1TB @ 5400

I'd like to put a low-budget card in, something like an Nvidia 550ti or maybe 650 if it could handle it? Is it even possible to put a card in this machine. I assume that is depends on the MOBO having the necessary slot for it. Just wondering if any of the techies on here know about this sort of situation. It is a retail machine (grrr couldn't talk the parents into letting me custom build) so it might be a pain to replace even if its possible. Thoughts?

I'm unsure if your if your mobo can even handle a 550 and even if it could, there's no point having a decent gpu but horrible cpu, it's the same as buying really good tires for your car, but your car is garbage so even if it is good, it's too unbalanced.

With those specs you should just save up for a new custom computer. And also, considering how old those specs are, i doubt your psu can handle a 550ti, but then again ya never know.