A whole lot of digital mode operations are adapted from CW. Bear in mind
though, a lot of it is out of lazy typing rather than good operating
practice. It is always best to be clear. Use English properly and simply
to avoid confusion. For contest operation it is usually specific to the
contest.

The interface technology is similar for most of the sound card type modes.
You need to understand attenuators and impedance transformation theory but
there are particulars for individual models of radio.

Rig control is different and usually involves a serial interface rather than
audio interface, but again is specific to adapt to the radio. The change to
USB ports is a complication. Rf energy in the shack brings other problems
into the mix.

Google is your friend. There are volumes on the various subjects. There is
usually a learning curve because of the specific needs of your particular
station. My setup is a bit crude but ever evolving. I have found
transformer coupling with proper attenuation to deal with impedance matching
and common mode interference issues. I keep threatening to build it all
into a small box complete with automatic audio source selection with level
control, RX out buffered to different outputs and data switching. Look into
MFJ and RigBlaster for store bought solutions that are highly adaptable to a
variety of rigs and situations.

I'm also looking for information about how to harness my PSK software
to drive my logging software so I don't have to keep manually entering
all the log data. What software is out there that does this, and
where can I find it?

Look at logging programs that fetch the band, frequency and maybe mode from
the rig control port. All you need to do is paste the callsign in from PSK.
I bought LogEQF quite a while ago and like the readability and speed of it,
but it's kind of a personal thing depending on how you set up the other
stuff too.

I like to make timestamp macros in the whatever Digi software, so that the
timestamp will be put into the QSO as a redundancy and all gets saved to
cache.