Yeah, at least if you get them together, you know they'll be compatable. Just watch out that you don't get scammed into buying something less powerful for your money.
As for AMD 64 processors, these range in two sockets, 754, and 939 depending on the speed, and core (the core is what is used to power it. 939 sockets for example are for Winchester cores and 754 are for the rest I think, and just involve different manufacturing processes (939 uses a 90 nano metre 'nm' process), which doesn't affect performance much, though 939 socket processors tend to run cooler, and so if you see a 3200+ AMD processor with a 754 core and a 939 core Winchester, you will know what it's about))
So make sure you get a motherboard that matches the socket 754, & 939 to the processor you will get, and you should be fine. It is also best to check the support in mhz rating.
Now if you don't know this, it is very helpful.
Pentiums use a different method of mhz and ghz ratings (1000mmegahertz = 1gigahertz) and this is how fast the processor can clock information. Now Pentiums you will find are scaled in numbers like 2.5ghz and 3.0ghz, 3.5ghz etc while AMD's are in numbers like 2500+,3000+, 3200+, 3500+,etc which means that in terms of power these will be as good or better in terms of speed at some tasks than a Pentium at these rated mhz ratings.
If you look at an AMD processor for example at 3500+ but is only has a 2.2ghz processor stated, don't be alarmed, as this will run as fast as a 3.5ghz pentium, but in AMD terms, it only runs at 2.2Ghz.
This is because AMD's use a different way of processing tasks and so one clock gets more from the processor than if it was a Pentium
Most modern moterboard will have SATA aswell as but older ones will use IDE, and so will new ones.
I have always used IDE and I'm happy with it. With another inerface, your not going to get that much of a boost unless you spend loads on a drive, and so IDE is the cheaper alternative and is available on all PC's, and with hard drives anyway being as cheap as they are for alot of Gigabytes of storage, you can't do too badly
Most drives now run at 7200Rpm too which is the normal now for drives, though faster drives are available with 10,000Rpm speeds, but you will be expected to pay the premium for this technology. So IDE to me seems like your best bet.
With RAM it is a bit of a harder task, but just read the page, or ask the shop what sort of RAM it takes. It would take DDR, but there are speeds in DDR capablities, for example 3200 speed RAM and 4000 speed RAM. Most boards support 3200 speed and this seems to be the normal so watch when buying chips that you look at the rating, and also on the motherboard how many Gigabytes of memory it can take. 512mb to 1024mb seems to be the normal most people use for PC's, when the motherboard can maybe handle 2Gbs to 3Gbs (1024 a GB = 2048mb). If you can afford it, I'd go about half way in the capability to start with, so if it can support 2Gb, go for 1Gb of RAM ot 2 sticks of 512Mb
You might also find the word Dual Channel mentioned on some RAM sticks and also on some motherboards when you go searching.
What this means, is if you get RAM and a motherboard which supports this feature, you first get two sticks of the same rating of RAM you want (2x 512mb for example to make 1gb) and then connect these up in a special order on the motherboard. This then gives you higher speeds on the RAM chips than if you only used one RAM chip, or a board which didn't support it.
You will be expected to pay a premimum for this technology to, but don't worry too much about it, as I'm only explaining what they mean. Because if they support the feature, it is best to know how to go about getting it to work because RAM is what speeds your computer to work as fast as it should basically. The manual will tell you all anyway how to set this up if you do get compatable hardware
I hope this guide doesn't confuse you but rather guides you to find the ones you are looking for. If you have any more questions, don't be afraid to ask