What they said. Transfer in kind. All of your funds will be moved to the new company. Nothing will change. It will simply be a new company, old funds. Then you can go about selling off old funds and swapping to ETF's as it makes sense.
Depending on what funds you hold, some may not transfer in kind and will have to be liquidated before transfer. Those gains/loses you'll have to eat.
The good news is with Roths at least, you can sell all and swap with out any tax liability. Just don't remove it from the account. My retirement accounts are much cleaner this way.
I did this two years ago thought and it was the best move ever. So much more transparent, easier, and gains that match the market instead of being steadily just beneath it.