Replace Domains of ArcGIS 10.1

I need to Replace the Domain on Field level on my Geodatabase.

My Geodatabase having multiple features and tables where at each on field one Domain is assigned, I need to replace that Domain and Delete old domain.

To better way understand. (example)

1. Table1 having Field XYZ on which Domain A1 is assigned

now I like to replace A1 with A2 and once it change for all the tables I would like to delete A1 from my Domains.

I search on internet but I could not find any helping materials.

Do I do this with performing some query on database ?

select * from sde.GDB_ITEMS

Above query get me all the domains which exists for my Geodatabase but I could not to find relation how this domains is assigned to my tables (how's the relationship between them?)

I do believe that with that relationship I can replace the domain.

I am not python developer.. but I am trying to write this script..

>>> import arcpy 
... admin_workspace = "Database Connections/WGis01-SDE.sde" 
... arcpy.env.workspace = admin_workspace 
... domain_to_search = r"MM Work Function_1" #supply the CV domain name 
... datasets = arcpy.ListDatasets() 
... for dataset in datasets: 
... if dataset == N.Electric: 
... featureclasses = arcpy.ListFeatureClasses() 
... for featureclass in featureclasses: 
... print featureclass 
...

Parsing error IndentationError: expected an indented block (line 9) >>>

Please Help to get it done.