Hi Bullet,
As it is a triphylla, and of course I don't know how big it is, leave at least 6 inches of stems above soil level. You will find as the weather turns cooler a lot of the leaves will fall off anyway, but yes carefully remove all the old leaves left and give it a good clean, then spray against any pests that may be lurking on it.

You can pot-it-back if you wish, this means removing the bottom third of roots and putting it into a smaller pot. The reason for this, (a) it takes up less room, (b)it will encourage new roots to sprout, (c) being in a smaller pot and less soil, the risk of you giving it too much water is less.
If possible place it in a cool well lit room, keep just moist, NOT wet. A good idea is to place a plastic flower pot saucer underneath the pot and water it via the saucer, this way the moisture goes straight to the roots and the top half of the soil is kept drier compared to watering from the top. A lot of times people loose their fuchsias during the winter due to over watering. - Kath:)

Thanks, Kath! You're really a great help! As it is just a small plant (2' tall and 2' wide), I'll do what you suggested and bring it in.