Yes. We have just completed our changeover ourselves. It took about 7 weeks.
Briefly you need to change the angle of the headlights and have 2 fog lights. Take it to ITV in San Javier for test- similar to MOT - engineers report is part of it. Take every documentation you have from padron to residentia and original car documents.
Our car passed except for the tinted windows that we had done in Britain. We had receipt but not certificate. Britain is the only EU country that does not issue receipts. We came home and peeled off the film and they passed it next day.
Then go to Torre Pacheco tax office to pay similar to road tax.
Next we went to Cartagena to the Hacienda for a paper(not sure what for but needed it finally). We were told we needed to give proof that we had been living in Spain for only 5 weeks and advised to go to Alicante to the British Consulate. When we phoned them we were told a new office was opened in Murcia near IKEA. We went there and met with the honorary British Consulate guy who is a lawyer and got the next paper in the process.
Lastly we went to Trafico near the university in Cartagena, gave in papers and were told to return the next day. Wow! Imagine our delight when they gave us our Spanish number!
Everyone we met was so helpful and some even spoke English. We did however use google translate and placed a letter in front of the person we were dealing with if they spoke no English. Our friends had done it 2 years before us and showed us where to go but we went on our own with limited Spanish.
We had asked a group in San Javier for a quote and that was to be 600 euros not including the consulate part(150)
The total cost was 800 euros.