Do you use anything like amplitude for guitar?   

1. Can I easily use amplitude software on my desktop and run backing tracks or simply mp3 tracks (run through winamp, for example) so that I can play along with a track? 

2. My current desktop tower has two USB 3.0 ports on the front, which I'm hoping with suffice for an audio input device where I would plug in my guitar. I do not have firewire ports. That said, what device would hook up to USB 3.0 and offer the best value for my use?

I feel like I'm giving up on amps and pedals for the time being. PixxyLixxx videos on youtube helped.
I'm a regular Amplitube user both using its standalone app, as well as a plugin on my DAW.

On PC, if you're using your built in sound card w/ ASIO4All, your DAW or the Amplitube stand-alone would lock up audio from other sources. So you'd either have to import your backing track as an actual track into your DAW (or as of Amplitube 4, its own built in track recorder).

A couple of budget friendly / straight forward USB interfaces:
https://us.focusrite.com/usb-audio-interfaces/scarlett-solo OR the 2i2
Fender MIM Telecaster ('06) [Modded]
PRS S2 Custom 24 ('13) [Modded]
Squier Affinity Fat Strat [Modded]
Yamaha F310

Mesa/Boogie Lonestar 1x12 Combo
Mesa/Boogie Mark V:25

SD Vapor Trail
Xotic SL Drive
Xotic BB Preamp
Boss BD-2
Boss DS-1 [MonteAllums]
MXR 10-Band EQ