Q: Do you have to use a remote antenna? I saw some receivers had one included, but the one I purchased did not.
Some require a remote some do not, if you purchased it new and it didn't come with one then you are fine.
Q: Does the battery and switch harness hook up the same way as back in the 72Mhz days?
yep
Q: There is a long antenna and a short antenna on the receiver, what is the best orientation for these? Do they have to stick out of the plane?
just mount the receiver as you would, usually on a flat surface. They don't have to stick out, there's some special circumstances like certain recievers for carbon fuselages have longer antennas that do need to be outside a carbon fuse, but what you're talking about, no.
Q: What servos are compatible with Spektrum radios? For the PT-60 I intend to use just standard servos.
Standard servos are fine.
Q: Does anyone sell a flight pack any more that includes servos, receiver battery and switch?
Not that I'm aware of. Find yourself a Life Source or 5 cell nimh pack, best to stay away from the old 4 cell nickel packs in 2.4 installations