Anything IDE compatable (cd-drives, DVD, harddisk etc) is ussually interchangeable (except on servers which generally use SCSI; a different connection medium) between machines and certainly motherboards of a similar age (to some extent).
So unless the motherboard is retarded, it should support your old drives, and they are fairly easy to physically install and are automaticaly recognised.
RAM is a different story, the standards are prone to frequent change, the standard at the moment is DDR (Double Data Rate), although by the looks of the mother board you are getting it may support the old standard SD. SD was standard when the P3 was late, so say maybe around the 500mhz and 800mhz machines would use SD RAM.
However, bve cautious handling RAM as it is easy to damage or more likely destroy (due to electrostatic discharge).
as far as expansions are concerned, PCI has been the general expansion standard for the last however long, it's predecessor was EISA and previous to the at half the bit rate ISA. So all expansions should be compatible, you might have had a built in graf. card in your old machine, so your NEW motherboard doesn't have an on-board graf. card, your in trouble.
Although if your old machine had an AGP graf. card or PCI graf. card then you should be able to pull it out and use it in your new machine.
Although 2 AGP and 1 PCI? I've never seen that, I have 1 AGP and 8 PCI
I don't know why I typed all that, anyway, I agree with Dave, just watch out for that graf. card, because if you don't, you'll get your machine together, put it on your desk, plug in your power, mouse, keyboard and then when it gets to your monitor......