So based on some research and question-asking regarding a new budget GPU, I've decided on the Radeon HD 6670. My current GPU is an integrated Radeon HD 4200.
My computer is a Dell Inspiron 570, I bought it refurbished from a man for $100. Everything works as it should, but I'd like that new GPU and my current PSU can't handle it, so I've been told. My current PSU is this: HP-P3017F3 POWER SUPPLY DESKTOP POWER SUPPLY 300 WATT DELL
I heard from the same source that a PSU with around 500w would be perfect. I am however on a budget, and I know very little about PSUs. I've done my research on GPUs and found out how to install them, update drivers, and so forth, but the PSU remains a mystery to me. If anyone would recommend me a guide along the lines of "PSU installation" that'd be great.
So, to sum things up, I need:
1. A (budget) PSU which can run a Radeon 6670
2. To learn how to install this PSU