Need Help getting post-Brexit TIE

Hello, I have been living and working in Spain for almost 8 years and I'm in possession of the small green TIE. I now need to exchange this for the post-Brexit TIE to avoid issues when re-entering Spain. 
There's a lot of misinformation online and the process is very unclear. I believe I also need to register for the empadronamiento, which I need help with. I have a job contract and rent contract. 

If anybody is familiar with this process and can offer any help, I will be very grateful. I'm happy to pay for time/services offered. 

Thank you!