I recommend hiring a driver and a tour guide for this, it's nice to have guides for most things in India. One they can help you by pass lines & to there is just chaos outside of the Taj Mahal and its nice to have someone navigating you so you can turn your brain off. Plus, having someone tell you all the facts & take your picture is pretty great too.

Hotels
ITC- Save
Oberoi- Splurge

If you dont stay at the Oberoi, I recommend eating dinner here at the Esphesan if you plan to stay the night in Agra. There is not too much to do in Agra, you really go to see the Taj Mahal and that's about it. The drive from Dehli is about 3 hours and can get gnarly if you hit traffic (can take up to 6 hours). 

Another tip- if you want to avoid people at the Taj Mahal, try to arrive at sunrise!