I would recommend getting new soil and don't be afraid of having a high quantity of perlite/vermiculite and gravel. You want soil that doesn't retain much moisture, so avoid too high of a quantity of rich fertilizers, peat and clay. I also recommend getting it into the sunniest location you have in your house. If you're in the northern hemisphere, W and S are your best bet, West giving the most UV and hours of light per day.
The new growth may die back slightly from these conditions but it's okay: the new growth is weak and it's likely that trying to maintain the new growth in these conditions will only stress out the plant over time. I say it's better to just let the old die away and let the more resilient, hardy growth take over.