Is it possible to install snow leopard on a machine that has 10.5.8 on it?

Yes, if it's an intel Mac. Go to >About this Mac>More Info and see what the processor is.

The basic requirements for Snow Leopard are as follows:

An Apple computer with an Intel Processor
1GB of Memory (RAM)
5GB of hard drive space (Storage)
DVD drive for installation

1GB RAM is bare bones, you'd want more than that.

This is one of the biggest S.A. Apple retailers but I think it is a concession; that is, that Apple have no formal store. Hopefully they can supple the disk from there, but I can see problems. Apple S.A. does not appear to be listed in their Directory.