Uninstalling is quite easy. If you're dual-booting with Windows use a Windows boot disk and run fdisk /mbr or from Linux lilo -u (as root), but the second option will only work if LILO was installed only once (if you have changed your LILO configration, it will not work). If it's a Linux-only machine, you don't have to remove LILO.
Now you can remove the partitions (or only format them if you wish to keepr the scheme; if you have separate /home and wish to keep your configuration and files, don't format it).
All the partitioning can be done during SuSE installation, so the most important thing will be to boot it somehow.