What do i do with this ?

[hojo86]

Im new to the forum and need some advise on my Phal.

I rescued Zelda from the supermarket (yes I've named her Zelda and she's done really well over the few years I've had her) and she lives in my kitchen and flowered over the years from around February to around mid-August.
Ive never repotted her, or have ever drastically cut anything away .... apart from old or dead stalks etc.

Over the last few month Zelda looks terrible and as the pic shows has lost a load of leaves and her aerial roots look as though they want to escape the pot.

I think i have to repot ( actually I'm pretty sure) but im not sure how and where to cut?

Do i cut just under the browning trunk or get rid of the lot?

Do i try to put the aerial roots in the new potting medium?
What type of medium is best? Wood bark? (if so what type?) Soil? Pebbles? Sand????