If you decided to visit Astorga, consider a short stop at Hospital de Óbrigo to see the Puente (bridge) de Óbrigo. Both Astorga and the bridge are on the Camino de Santiago. Astorga isn’t that large. When we visited in 2017 there was a large free parking at the base of the town wall. From it you walk up the hill to the town.
We didn’t go into the Gaudi Palace. While the interior of the cathedral was less interesting to me than other cathedrals there are some very nice carvings on the exterior around the doors. The main plaza was worth walking through.
Another very minor site in the area is Crucero de San Toribio outside of San Justo de la Vega, between Hospital de Óbrigo and Astorga. It too is on the Camino de Santiago and affords a nice view of the area and nearby town.