replace? basic problem!?

How can I replace data from one table with data from an other one?

I have the following two tables:

Table 1: Persons:
-----------------
ID Name Furter information.....
1 Name1 ...
2 Name2 ...
.. ... ...


Table 2: Responsibility:
------------------------
ID Main_Res Assistant Further information
1 1 2 ...
2 3 1 ...
..

How can I retrieve the information of table 2, where the Main_Res and the Assistant information is replaced e.g. by the name of the corresponding person? The numbers in the columns Main_Res and Assistant correspond to the ID of the Person-Table.

Do you have a solution for this "simple" problem?