Welcome to the wonderful world of UAD. Sit down, let me take your coat. Girl, get him a drink. Martini, straight up, am I correct? Would you like a foot massage? Girl, massage his feet. Nevermind the smell. Comfortable? Good, nothing but the best at UAD.
The 710 is a mic pre with a/d conversion, but it is not an interface. It lacks the means to bring audio back out of software for playback, mixing, etc. You can use it with any interface, like the 2i2 or tascams I linked to.
I have the UAD Apollo Duo and I love that thing. It is my main interface. But be forewarned, when you're buying into UAD, you're buying into their plug-in scheme. It can get expensive and it never stops. Never. You'll keep buying plugs.
And, it isn't compatible with toys like garbageband.
The 710 isn't part of UAD's plug-in processor units, but it is still expensive and overkill if you're still contemplating the use of garageband. If you went with something like the Apollo, the investment alone shows a commitment to the art and you would need all other aspects of recording to be up to the task. That means your room, monitors, mics, etc.
If you want to stay with the idea of recording 2 channels for guitar and 1 vocal simultaneously, you should start with the Tascam for now. It is inexpensive, good and dependable. You'll learn a lot with what you want to do then maybe later on, you can decide if spending a lot of money is a wise choice or not.