Throw away and get a better one.

Of course can... question is where are u going to put it? I have seen people putting inside the glove compartment box or underneath the front passenger seat. But, why would u want to waste space / spend extra on wiring? The GPS on the stock player sucks. Just get something with Garmin if u seriously want GPS. Otherwise, get something better for sound and get a portable GPS.

Screw the GPS, u can get something like Sony DSX-S300BTX for RM 950 - no CD, uses iPod with storage and has USB flash drive support. BT is built-in. And I'm using it in my car. Display is 4 lines. Has BT audio so u can pair a tablet such as iPad and use it to watch movie in the car with sound coming from the car speakers.

If too much, settle for Sony MEX-BT4050U. Similar as above but display is 1 line, has CD and USB. BT audio also available. I had this on my car with swapping out for the above. Price around RM 650.

If u want BT, not much choice and usually above RM 500. Both are single DIN. Look around the forum, some may have 2 DIN for less than RM 1k with BT. I don't recommend 2 DIN with touch display... attractive to thieves.

Keep the HU. Later sure fetch high price when desperate owners need to sell the cars fast. I sold the original Myvi HU (1st Gen) for RM 250 some 2 years ago.