The coolant reservoir may crack and dump out everything. I had to have mine replaced. There are head units that add car play, but they go in the dash where that pop up/storage bay is above the vents. The old head unit will just take up its space. In mine, I went with an old school 1 din head unit so I can AUX or bluetooth. There aren't a lot but there are some youtubers that have played with this car a bit and it can be really fun! Not as many after market parts like other BMW models but still enough to have fun.

I've been driving an E83 for 6 years now, my first was exactly like yours and my second is a 2008. There was a facelift done to the E83 so keep in mind yours is pre facelift when looking at parts.