I am pretty much parrotting a lot of what Moose has already told you, but Southern PA is very, very similar to MD (which you imply you’ve already hiked). It has lots of ridge walking, which, in turn, means that there are occassional rocks (though nothing like you will see further north in PA) and that water can be a problem, especially this year since rainfall has been way below normal (Hopefully, by the time you get out there, this will have changed).
Aside from the occassional rocky sections, the trail is quite easy here. I highly doubt it ever gets above 2000 feet above sea level at any point, so the ascents and descents are quite easy. Generally, you will hit a major gap every ten miles or so, but the climb down and back out is rarely more than 500 vertical feet so there is little to fear. Of course, this low elevation means that the views/scenery, while still great, will simply not compare to what you can see further north or south (again, MD is a good comparison with regard to this).
This section also contains several local and/or state parks (Pen Mar Park, Caledonia State Park, Old Forge Picnic Ground, etc., etc.). These are useful for replenishing water supplies; taking a break; and for getting a nice, high-fat meal without getting too far off the trail. If you don’t happen to be near a park, you will still rarely be more than a few miles from a well-traveled road crossing from which you can walk and/or hitch to a store for resupply and/or a good meal.
I haven’t really researched off-trail lodging in this stretch, so I can’t help much. I know that the trail essentially parallels I-81 in this area and I-81 has a couple of hotels at almost every off-ramp so until you cross the Cumberland Valley, you will likely always be within a few mile hitch of a hotel. After you cross the Cumberland Valley, there is the infamous Doyle Hotel in Duncannon and the Port Clinton Hotel in Port Clinton. I haven’t stayed in either so I cannot vouch for them, but I know the Doyle is considered a must-see for hikers due to the tremendous amount of “character” it possesses along with the fact that it is very cheap, convenient and hiker-friendly. I don’t think the Port Clinton Hotel is quite so hiker-friendly nowadays so I would recommend you research it more before deciding to stay there.
By the way, if you are a history buff and you have time to spare, you will pass quite close (within 10 miles or so) to Gettysburg National Battlefield. It is well worth long hitch and potential time lost. Simply follow PA Route 30 east (which ironically follows the route that much of the Confederate army took to Gettysburg in 1863) and it takes you right through the battlefield and into town.
FYI, winter has pretty much skipped this part of the world so far this season. Assuming this anomalously warm weather continues, you can expect that, due to the lack of a real, varmint-killing cold spell, there will be lots and lots of bugs, mice and other undesirable critters on the trail and at shelters.
Ken G.