Hi Yuga,
Yes, I'm talking about reconfiguring your database and database engine, not the SAP installation. You can do this without any data loss, although there will be some downtime.
To move the database or transaction log files, you need to shut down the SAP application, then use the SQL Server Management Studio to detach the database. Then move or copy the files to the new locations you want, then back in the Management Studio attach the database specifying the new file locations. This can be done using the Management Studio's GUI, or via query commands (also via the Management Studio).
To move TempDB is slightly more complex, in that you must use alter database query commands to define the new file locations, and then you must restart SQL Server for it to take effect.
After you have done these things, you can restart the SAP application.
Changing the recovery mode from SIMPLE to FULL can be done while everything is online. Afterwards, you must get a full backup of the database before you can start getting transaction log backups, and you must ensure that you get regular transaction log backups (not only to protect yourself against data loss, but also to prevent the transaction log from becoming full). The recovery mode change itself is made via the database properties dialog in the Management Studio.
Have a look at Note 363018 for a description of the procedure for moving database, log, and tempdb files. It is based on an older version of SQL Server, SQL 7.0, and you can do some of it now via the Management Studio instead of all being query commands, but the query commands described will also work just fine.
Also, look at http://service.sap.com/instguides -> Database Upgrades -> MS SQL Server for access to installation and upgrade guides for SQL Server releases 2000, 2005, 2008, and 2012. The guides are well-written and include SAP's installation recommendations.
I also recommend having a look at my own blogs SQL Server 2012 Installation Recommendations and SQL Server Configuration: Pre-SAP Installation. The first one in particular includes a list of useful SAP Notes about configuring SQL Server.
There are many useful documents and blogs in the SAP on SQL Server space that you will find helpful, as well.
Regards,
Matt