create a new web application and a temp site collection - the site collection should have the same template as the one your going to overwrite it with (e.g. team site)
once that is done, use powershell to backup the site collection and use restore to restore over the temp site collection you created in the first step within the new web application.
Backup-SPSite (site collection level)
Backup-SPSite http://tempsite:12345/sites/mysite -Path C:\Backup\site_name.bak
Restore-SPSite (Site collection level)
Restore-SPSite http://tempsite:54321/sites/mysite -Path C:\Backup\site_name.bak
no its not possible, the backup and restore is full fidelity, that means it keeps alerts and workflows but it also means that the ID's are the same so it would cause a conflict and fail on restoring! you could give it a try tho but will lead to dissapointment.
The only guid that changes is the root site level which is the origional site collection level that you create that is overwriten.
but what your refering to is different, that can be achived by using the copy function:
Copy-SPSite http://contoso/sites/OldTeam -DestinationDatabase WSS_Content -TargetUrl http://contoso/sites/NewTeam
giving a new name, the method above... dont create a new site collection within the web application, rather only run the powershell code, the targeturl you copy the source url location but rename it to the site url you want eg.
source url : http://mysitepage.com/sites/origionalSite
destination url : http://mysitepage.com/sites/MyNewSiteURL
so my new copy of the source site is now called MyNewSiteURL.
Copy-SPSite http://mysitepage.com/sites/origionalSite -DestinationDatabase WSS_Content -TargetUrl http://mysitepage.com/sites/MyNewSiteURL
there is no copysite in sharepoint 2010 but what we do have is export and import. This tho is not full fidelity and will generate new GUIDS for lists and web objects, all associations are lost like alerts and workflows!
Export-SPWeb [-Identity] -Path
[-AppLogFilePath ] [-AssignmentCollection
] [-CompressionSize ] [-Confirm
] [-Force ] [-HaltOnError
] [-HaltOnWarning ]
[-IncludeUserSecurity ] [-IncludeVersions ] [-ItemUrl ]
[-NoFileCompression ] [-NoLogFile ]
[-UseSqlSnapshot ] [-WhatIf ]
url above shows its for 2013 but same applies for 2010!
you can export at sitecollection level, site level or document level.... all depends on the url you give. In your case you want to export a specific site than you would do the following:
Export-SPWeb -Identity http://mysitepage.com/sites/origionalSite -Path C:\Backup\site_name.bak -Force
Import-SPWeb -Identity http://mysitepage.com/sites/MyNewSiteURL -Path C:\Backup\site_name.bak -Force