Doesn't your camera come with a conversion tool of it's own!
My Sony for example does!
I guess the best way is to eventually convert to mpeg 2, in the original resolution and highest possible bitrate to prevent qualtiy loss.
Best to just test the different converters, and go with the one that gives you the best results!
Otherwise use a googlesearch on converters, so you'll get more direct feedback.
Maybe other users of your camera already came up with a solution!!
Mpeg2 is much less stressfull for your computer, as AVCHD demands a really powerfull computer!
If i understand correctly you can put your clips on the timeline!
Do you get question marks then, or does studio prevent putting the files on the timeline all together?
Do the clips preview in Studio?
Can you watch those clips on your computer with a Third party player off some sort?