Before replacing take necessary steps to protect ur valuable data / info first, cause OS can be installed, but if u lost ur data u can not get back again it easily.....
1. Backup ur data to a CD /DVD / Flash Drive (with good ones) and it is safe to take the same whole data to another storage device.
2. Write down all necessary conf of ur laptop that helps to configure next time after install OS like IP add, Gateway, special service(if any), PATH settings, Browser setup(if any) etc.
Now ur next Q, "Will the original disk boot to the hard -drive? It is Linux lite" , every OS (like Linux / Mac / Wind or other OS) has capability to boot computer specially in case of Linux with its strong GRUB utility. Whatever Linux OS u installed, it can boot and take u to the Desktop environment that u can work smoothly. Just take care when u installing Linux, specially during time of installing. Look after the Partition related Q / u can customize the set up. As u mentioned Newbie, it is better to take help from an expert person and learn how he/she installed and do other conf during setup.