Hi Bellan and Welcome,
Yes to all your questions!
You can record your own voice, you can even have many different voice recordings (for instance different people in the family) and have them play back at random or select one specific set. I sometimes put sound off and read the cards to my baby and talk about the pictures, and sometimes have sound on, but still do some talking. I personally feel that it's important for my baby to hear a live voice with interaction too, but the children voices + other sound effects adds to the multisensory learning experience and makes it fun for my baby.
For the math quantities, you can have a tiny number in the bottom so you can tell your baby the quantities and don't need sound. I only created one sound set and it took me close to 2 hours. You have to record numbers 0..100, +, -, x, \ and =. Before that, I use to read the numbers because I'm doing math in Afrikaans.
Little Reader also takes quite some time to translate, but if you're not doing voice recordings, it wouldn't be that long.
Little Reader / Little Math comes with a voice recorder application.
Check out these links for how to translate your LR and LM courses:
http://support.brillkids.com/entries/20622132-how-can-i-translate-my-little-reader-english-curriculum-into-the-language-i-want-to-teachhttp://support.brillkids.com/entries/20585972-how-to-use-different-language-sound-sets-in-little-mathBrill Kids have very nicely planned out courses for both English and Chinese, but if you translate thier catagories as is described in the links above, you'll still have to plan your lessons day by day. There is currently a Playlist functionality to help you with that, but only the upcoming Little Reader version (LR v3) will allow you to build a proper Swedish course (with lessons planed for each day.)
For LM you can play the lessons in Swedish then replay them in English again at any time, it's all just a question of quick settings to be changed and selecting the lesson you want to play and can be done in seconds.
For Little Reader, many parents do both English and Chinese at the same time, some even do multiple languages at the same time.
Hope this helps.