Please carry a list of your medications with you when you see a lung specialist (or whoever does the appointment for your sleep apnea test). If there are any meds that the doctor thinks might influence a sleep apnea test, he will tell you.

As for the dryness, yes, it can occur, but if you use clear, fresh pure
water in the humidity portion of the machine each night, you'll have plenty of moist air coming your way.

The major benefit of CPAP therapy is that it supplies the REM (rapid-eye movement) sleep that charges our "batteries". And it does reduce or even eliminate the times that you feel you need an afternoon nap.

It does not act as an insomnia solution, however. I still have to take
an antihistamine at times to relieve high histamine levels that interfere with
sleep. I will be surprised if it eliminates all insomnia for you, but you'll just
have to wait and see or ask your specialist about it.

I hope it works for you. I like the Resmed CPAP equipment personally,
but there are, as others have said, many types out there. (It's covered by Medicare, and for you, your health insurance probably will cover it.)

Good wishes and good sleeping!