50 to create.
Shields cannot be repaired in the Astral, you need to return to the hangar in order to do that.
When choosing the combination of shields, it is important to have a balance between their Power and Recovery rate. Higher Power is important for front and rear shields - rear shield will usually take the most damage, while the front will need to withstand a lot of damage if you decide to ram a demon (or to provide additional Power for Balancing shields through the Visor). Higher Recovery Rate is more important to the side shields - they will usually need to be restored fast after a cannon fight. Different players use different combinations according to their tactics.