Miguel in Roquetes can arrange it for you, .  He did ours.  To get to his garage go towards Roquetes from the Corona roundabout in Tortosa, straight across at the next roundabout, then look for the Da Vinci bar on the right and turn right down the road next to this.  Miguel's garage is straight ahead on the right at the crossroads.

Ours was done about 5 years ago and at that time cost about 700€.  Costs can be variable depending upon the value of the car when it was imported into the country.  No doubt it can be done cheaper but then you will need to finc a technico to give a report on the car, a gestor to do the paperwork, maybe trips to Tarragona etc.

With regard to the lights we were able to change to Spanish plates just using deflectors.

Our Kangoo cost about €400 to matriculate (we used somebody to cut through the red tape) plus €50 for a pair of second hand Spanish rear light clusters.The BASE didn't even know the value of probably the commonest car on the road for import tax purposes,so we exstimated it,rather well.....
(Car cost £1850 in UK,equivalent over here €4000.)