I have used LEVC.
The GA parking is away from the terminal. However, there is an exit there. If you have already cleared customs in Spain you should be able to use it. Otherwise you need to use ground handling - not that expensive.
The GA terminal is NOT the main terminal building. You cen get all your weather and file then handling will collect you from there.
Queue can be long for fuel. I never had any problems using a Credit card. Fuel cost differs by the amount you purchase - e.g. gets cheper the more you buy.
Like the rest of Spain, nothing happens quickly.
I have also used Zaragosa - quiet, empty, fuelled quickly.
San Sabastian - again quiet, empty, got fuel quickly. Interesting place to land, mountains around you!
Enjoy your trip.
Tim.