Mass Effect

So I recently started re-watching Babylon5 while listening to a couple of podcasts "Babylon 5 for the first time" and "Grey 17." Some of the hosts seem to be big fans of Mass Effect and see lots of similarities and parallels between the two series, which piqued my interest.

The last time I seriously gamed was Diablo 2, Sid Meier's Pirates, Quake era, figure 20 some-odd years ago. My assets are, a halfway decent laptop, a bunch of desktops of varying levels with nice monitors but nothing special for the graphics cards, and a willingness to spend a few bucks for a good experience.

How fancy of a computer do I need? I'd prefer not to get a console, but if that would be better I'm open to it.

Will I be able to play with keyboard and mouse, or do I need a joystick or gamepad or something?

What is the best way to obtain a copy? Steam? Ebay?

I'd prefer to not be spoiled too much, but is there anything I should know before I start?

Thanks!