Alpine Vehicle Hub Pro with Nav TV interface to the factory screen. It's pricey but effective, although no one to my knowledge has actually tried it. Nissan never made any options for us to even be able to play MP3 CDs unfortunatly
. Acording to the FSM there are Aux pins in the loom but no actual connection to plug into, i.e. phono.
Other than that you'd be looking at custom. Check out Darren's thread in the members section as he has moved the controls down into where the cubby hole and cd player are which has left a double-DIN space above. With that you can put in your own headunit then. I believe the ISO for the phase 1 (2000-2002) Almera works with the CD drive on the phase 2 (what you have) but I cannot confirm. If you don't have Sat Nav then you could try this. If you do have Sat Nav then you could move the nav drive backwards to leave space (what I intend to do), as you rarely need to access the disc in the drive (Nissan not being very efficent with space there!!).
I hope that helps and puts you in the right driection
. Oh and welcome to the club
.
Darren's thread:
http://www.almeraowners.com/showthread.php?t=26434&page=10