If you google Knit Nativity

If you google Knit Nativity patterns you will get many sites about such patterns.  I know that Jean Greenhowe, a famous English designer of knitted dolls and toys has such a pattern sent.  I believe that Alan Dart and maybe Jan Messent also have designed such sets.  And when I did a quick google search, apparently Leisure Arts has a nativity pattern.Depending upon when your grandmother knitted your set, she may have used an older pattern.  You don't necessarily need a pattern if you are doing repairs.  Depending upon the degree of damage, you may be able to do repairs using an embroidery stitch work called duplicate stitch or Swiss Darning.  Again, google either of these terms for websites with tutorials on how to do the duplicate stitch.