I have just finished adding a Kenwood KIV-700 to my GT today so can answer your questions:
1) The Alfa headunit does not have a cage but I assume a cage will come with your Pioneer unit and that will slide straight in, with a bit of force
2) I too have a mic for bluetooth and found it very easy to run the cable from the unit to above the windscreen (didn't quite have enough cable to reach the interior light). You just need to loosen off the panels either side of the steering wheel run the cable through and then run it up the pillars. I used a plastic implement (like a knife) to push the cable into the lining that runs up the pillar and this worked very well.
Hope that helps.
Ray
1) The Alfa headunit does not have a cage but I assume a cage will come with your Pioneer unit and that will slide straight in, with a bit of force
2) I too have a mic for bluetooth and found it very easy to run the cable from the unit to above the windscreen (didn't quite have enough cable to reach the interior light). You just need to loosen off the panels either side of the steering wheel run the cable through and then run it up the pillars. I used a plastic implement (like a knife) to push the cable into the lining that runs up the pillar and this worked very well.
Hope that helps.
Ray
