Relining a favorite coat or jacket is not as difficult as you might think.  Begin by studying how the lining looks in your jacket; then carefully remove the lining by ripping the stitches connecting the lining to the facings and hems.  Take the lining apart at the seams; press and use the pieces as the pattern to cut a new lining.  Construct the lining.  The easiest way to insert it into the jacket is to sew the lining to the jacket facing and finish the hems by hand.