Installation of a single antenna would be easier... if only because there are fewer steps. But two antennas can be mounted on the same mast, so the task is still manageable in most cases.
Finding 10' mast section sold as 'TV antenna mast' can be a challenge but for the size antennas I've suggested, you can use chain-link fence 'top rail'. Example,
http://www.homedepot.com/p/YARDGARD-...2#.UWBJBDd49Ss
Gable/Eve, Wall, Chimney and Tripod mounts are all excellent choices for supporting the mast without guy wires. I tend to favor the chimney and eve options, you can usually see the underlying material that you are attaching to, so you can be sure you're connecting to something solid.
http://www.3starinc.com/antenna_mounts_and_masts.html
http://www.solidsignal.com/cview.asp...ing%20Supplies
In this case, the H-VHF signals are weaker so I would place the H-VHF antenna at the top of the mast, the UHF antenna would mount about 4' lower on the mast. The combiner can mount on the mast as well, so you only have one cable to run from the mast to the TV (or splitter).
Here are some links to generic installation guides and related information,
http://forum.tvfool.com/showthread.php?t=901