Server Cluster & RAID HDD

put together a high availability cluster for a PHP + MySQL based app to run on a LAN. We're going to use Linux, and cost is a major consern. The app itself doesn't use / need too much resources, as it will only be accessed by 2 / 3 people at a time, so I'm using the following:

2 identical PC's with:
3Ghz PIV CPU
1GB RAM
2x SATAII 160GB HDD space setup as RAID 1
10/100 Mbps LAN NIC's, on a 100MB 8 port switch

Up to now I have been running MySQL-Max 5.0.15 to run a MySQL master-master replication server, which works fine, but the setup involved a lot of manual work, and downloading of the right binaries.

Furthermore I used Linux Heartbeat todo auto switchover between the two servers & RSYNC to sync the application files between the two. This has been working fine untill one of the server's HDD's failed recently corrupting both HDD's

So, I need a better way of doing this, and want to meet the following requirements:
If 1 HDD fails on either server, the server still needs to be able to run without a problem.
Replacing a HDD & rebuilding the RAID array should be easy to manage, preferabbly over the net.

Setting up a cluster should be easy to manage, both for the MySQL DB server & the files that need to be synced between the two machines Re-installing the server should be easy todo as well.

For No.1 I have been thinking of setting up RAID 5 with 4x HDD's - how reliable / safe / redundant is this?

For No. 4 I have been thinking of using something like sysimager to backup the server once setup, but will / can it recreate the RAID array upon restoration? The MySQL DB & PHP files are being backed up to a removable HDD on a daily basis.

The client is 700Km's away, so we can't just drop-in to fix things as often as we like. Thus redundancy is of utter importance. Currently I'm running Suse 9.3, simply due to the fact that it's easy enough to tell the client over the phone howto do things with YaST. Suse 10.1 will be used for the new setup, but I could also use Fedora Core 5, and have also been thinking of using SME server 7.0.