OS upgrade

Sorry for my 2nd post in a day but I'm after some advice again.

I have a server with 8 disks. Disk 0 is not RAIDed the others are. 
Disk is the system disk with /, swap, boot on. The OS is FC4.

The RAID partition uses LVM and is about 1.8Tb, 1TB in use.

I want to upgrade, or re-install with CentOS and I don't want to have 
to re-store all data on the RAID 5 volume but I am not sure that I 
can because the LVM will use files from the system disk.

Am I going to be able to maintain my existing LVM volumes during the 
re-install? Is there a procedure to maintain LVM or store in after an 
install or upgrade?

The system is backed but if I have to re-create the partitions and 
restore it will be off-line for several days and I would need to 
schedule it for a public holiday.

Any advice. Thanx,
Dp.