hello developers...
I'm a salesforce newbie. I have a requirement where I need to replace standard new button on lead object with a vf page. Below is my vf code...

<apex:page standardcontroller="Lead" tabstyle="Lead" extensions="ExtensionClass">
 
 <apex:form>
 
 <apex:sectionheader title="Lead Edit" subtitle="{!if(Lead.Id==null,'New Lead',Lead.Name)}"></apex:sectionheader>
 
 <apex:pageblock mode="edit" id="leadPB" title="Lead Edit">
 
 <apex:pageblockbuttons>
 <apex:commandbutton action="{!save}" value="Save"></apex:commandbutton>
 <apex:commandbutton action="{!cancel}" value="Cancel"></apex:commandbutton>
 </apex:pageblockbuttons>
 
 <apex:pagemessages></apex:pagemessages> <!-- displays all message generated by the component -->
 
 <apex:pageblocksection id="LeadInformationPBS" title="Lead Information">
 <apex:inputField value="{!Lead.OwnerId}"/> 
 <apex:inputfield value="{!Lead.Phone}"></apex:inputfield>

 <apex:pageblocksectionitem>
 <apex:outputlabel value="{!$ObjectType.Lead.Fields.FirstName.label}"></apex:outputlabel>
 <apex:outputpanel>
 <apex:inputfield value="{!Lead.Salutation}"></apex:inputfield>
 <apex:inputfield value="{!Lead.FirstName}"></apex:inputfield>
 </apex:outputpanel>
 </apex:pageblocksectionitem>
 <apex:inputfield value="{!Lead.MobilePhone}"></apex:inputfield>
 
 <apex:inputfield value="{!Lead.LastName}"></apex:inputfield>
 <apex:inputfield value="{!Lead.Fax}"></apex:inputfield>
 
 <apex:inputField value="{!Lead.Company}" />
 <apex:inputfield value="{!Lead.Email}" required="true"></apex:inputfield>
 
 <apex:inputfield value="{!Lead.Title}"></apex:inputfield>
 <apex:inputfield value="{!Lead.Website}"></apex:inputfield>
 
 <apex:inputfield value="{!Lead.Leadsource}"></apex:inputfield>
 <apex:inputfield value="{!Lead.Status}"></apex:inputfield>

 <apex:inputfield value="{!Lead.Rating}"></apex:inputfield>
 
 <apex:inputfield value="{!Lead.Industry}"></apex:inputfield>
 <apex:inputfield value="{!Lead.NumberOfEmployees}"></apex:inputfield>
     <apex:actionRegion >
         Target Sectors:  <apex:inputfield value="{!Lead.Target_Sectors__c}">
                                      <apex:actionSupport event="onchange" rerender="TargetSector,theMessage"/> 
                                      </apex:inputfield>
                                  </apex:actionRegion>
      <apex:outputPanel id="TargetSector">
                      <apex:pageBlockSection id="ProdFamily"  rendered="{!IF(Lead.Target_Sectors__c == 'Other', true, false)}"> 
                            <apex:inputfield value="{!Lead.Please_specify_the_Other_reason__c}"/>
                 </apex:pageBlockSection> 
    </apex:outputPanel> 
 </apex:pageblocksection>
 
 <apex:pageblocksection id="AddressInformationPBS" title="Address Information" columns="2">
 <apex:inputfield value="{!Lead.Street}"></apex:inputfield>
 <apex:outputtext value=""></apex:outputtext>
 
  <apex:inputfield value="{!Lead.Website}"></apex:inputfield>
 <apex:outputtext value=""></apex:outputtext>
 
 <apex:inputfield value="{!Lead.City}"></apex:inputfield>
 <apex:outputtext value=""></apex:outputtext>
 
 <apex:inputfield value="{!Lead.State}"></apex:inputfield>
 <apex:outputtext value=""></apex:outputtext>
 
 <apex:inputfield value="{!Lead.PostalCode}"></apex:inputfield>
 <apex:outputtext value=""></apex:outputtext>
 
 <apex:inputfield value="{!Lead.Country}"></apex:inputfield>
 <apex:outputtext value=""></apex:outputtext> 
 </apex:pageblocksection>
 
 <apex:pageblocksection id="AdditionalInformationPBS" title="Additional Information">
 <apex:inputfield value="{!Lead.ProductInterest__c}"></apex:inputfield>
 <apex:inputfield value="{!Lead.CurrentGenerators__c}"></apex:inputfield>
 
 <apex:inputfield value="{!Lead.SICCode__c}"></apex:inputfield>
 <apex:inputfield value="{!Lead.Primary__c}"></apex:inputfield>
 
 <apex:inputfield value="{!Lead.NumberofLocations__c}"></apex:inputfield>
 </apex:pageblocksection>
 
 <apex:pageblocksection id="DescriptionInformationPBS" title="DescriptionInformation">
 <apex:inputfield value="{!Lead.Description}"></apex:inputfield>
 </apex:pageblocksection>
 
 <apex:pageblocksection id="OptionPBS" title="Lead Information">
 <!-- If you want to have a checkbox to implement whether to use Active Assignment rules you will need to create your own using a custom Apex Extension and method -->
 </apex:pageblocksection>
 
 </apex:pageblock>
 
 </apex:form>
 
</apex:page>

In the above code, I need help for some functionalities.
 1) Can you please help me with Target sector field to get indented neatly with the page as it is showing as separate block in the page(please view this in your DE for clear understanding)
2) Can you please help me with save & new button along with custom extension
3) Can you please help me with displaying "Assign using active checkbox" in the vf page.
    
Thanks in advance
KK