SQL & PL/SQL :: Load Data From Table A To B While Looking Up Value From C?

I am very much new to this vast world of Pl/SQL. Recently I have moved to pl/sql domain. I want to write a package to move data from Table A to Table B by looking up the table C. Bellow is skeleton of my package.

Table name: source_a
columns: X1,X2,X3,X4,X5
Target table name: target_b
columns:Y1,Y2,Y3,Y4,Y5
Lookup Table : lookup_c
columns : Z1,Z2,Z3,Z4,Z5

1) I have to load data from source_a to target_b.
2) If value of column X1(source_a) matched with value of column Z1( lookup_c) then only we will process the recordsmeans those records will be the valid records. Rest of the records will be dropped.
3) From the valid records If X2 != Z2 then call a procedure pk_rec.generate_Y2(X2) to generate the value of Y2
{pk_rec.generate_Y2 already existing no need to create) else take the records form Z2 and use it to load the y2.
4) From the valid records If X3 != Z3 then call a procedure pk_rec.generate_Y3(X3) to generate the value of Y3
{pk_rec.generate_Y3 already existing no need to create) else take the records form Z3 and use it to load the y3.
5) X4,X5 are directly loaded into Y4,Y5.