Here is a code snippet hoping that someone blessed with Android Knowledge wud answer my query...
continuePreference.xml
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android" >
<PreferenceCategory android:title="@string/softwareUpdate">
<Preference android:key="continueUpdate"
android:title="@string/continueUpdate"
android:dialogTitle="@string/continueUpdate" />
</PreferenceCategory>
</PreferenceScreen>
checkPreference.xml
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android" >
<PreferenceCategory android:title="@string/softwareUpdate">
<Preference android:key="checkUpdate"
android:title="@string/checkUpdate"
android:dialogTitle="@string/checkUpdate" />
</PreferenceCategory>
</PreferenceScreen>
Now in code, HelloAndroid.java
addPrefrencesFromResource(R.xml.checkpreference);
...
...
if(ok) //Expected Output: To replace checkPreference with continuePreference screen.
addPrefrencesFromResource(R.xml.continuepreference ); //Actual Output: Results in Screen break i.e., appending with previous screen.

...
...
Whereas if Preference Screen is loaded through code then,
setPreferenceScreen(mPS1);
...
...
if(ok) //Expected Output: To replace checkPreference with continuePreference screen.
setPreferenceScreen(mPS2); //Actual Output: Same as Expected Output
Please do let me know how do I replace the preference screen through xml.