1). I'd recommend the following (using Khmer as the example):
- First, you'll need to find a private tutor or language partner who speaks Khmer natively. For that, I'd suggest iTalki.com
- Get a list of example words. Bonus points if it's a set of examples for each letter/sound of the alphabet, since you'll be able to turn those words into spelling flashcards. You might be able to show your tutor the alphabet you're working off of and have them come up with example words on the spot.
- Have your teacher say each example word.
- Then you say each of the example words.
- Your teacher listens for mistakes, and then you record your teacher:
a) Impersonating you making that mistake
b) Saying the word correctly.
- Now create minimal pairs from your teacher's recordings where your goal is to know whether the teacher is saying the word correctly or incorrectly.
- As for turning those audio files into individual sound files, there's a little guide for that at the bottom of the page here: http://fluent-forever.com/chapter3/ that uses the free audio program Audacity.
- For recording your teacher, there are a bunch of apps that let you record Skype calls.