XPS 8300, upgrades guidance

So my home computer has been a stock XPS 8300 from 2011-ish. It hasn't given me any problems so I've never done anything with it. As she's coming round to her decennial anniversary, I want to upgrade to extend her life. My computing needs aren't too demanding as I do admin, internet research, etc. for the most part with casual gaming, and there is starting to be some lag . In the next couple years I'm assuming my son will want to play games on it as well, so I'd like to give it a fighter's chance if possible. It runs Win7 and I am not looking to upgrade, instead running Linux and dual booting for when I need to jump back to Windows for something.

Currently under the hood -

CPU: Intel Core i7-2600

GPU: Nvidia GeForce GT 530

HDD: WD Blue 500GB (2010) (vulnerable to failing according to Dell software and HDD Scan)

RAM: Nanya NT2GC64B88B0NF-CG 4x2GB

I currently run two monitors: Dell S2440L (HDMI) and Dell ST2320L (VGA), both 1920 x 1080 at 60 Hz.

From my entirely uneducated point of view, gotta bump up to a SSD (possibly considering Crucial MX500 1TB but am open to all suggestions).

From everything I'm reading RAM is good at 4x2GB, though watching resource monitor I can have a 2-3 gigs of Standby memory at times, and right now 5.7 is in use for Chrome, a Word doc, and a PDF.

I would like to put in a new GPU, but am unsure of compatibility issues due to how old the motherboard is and no knowing if the PSU will get it done.

Any advice would be greatly appreciated. Apologies for not being able to be more specific on the parts I'm looking for.