Hello,
I know apple is so stupid with their prices. Currently the only way to fix this is to take it to apple or give it to a 3rd party that uses a laser that melts the extremely strong adhesive on the glass. I dont think that giving it to a 3rd party to fix will lag the phone, it might affect the water resistance (its always a good practice to keep your devices away from water and other liquids)but i dont think dust might be a big problem if they install the new backing right. Perosnally i would take it to a 3rd party to get it fixed as my iphone xs back is cracked too but I haven’t gotten around to give to a repair shop to repair it. Jerryrigeverything has a video on the laser removing the adhesive and its pretty cool. Heres the video if you want to watch the process https://www.youtube.com/watch?v=Lj4Od9D4puc&t=463s