Both should be possible, I'm not sure of your make though. What type of machine is it?
I upgraded the memory in my Compaq laptop to 512Mb, but the thing to be careful about is that many laptops use proprietary RAM, so you have to buy it from them and it's usually more expensive. I was lucky that generic RAM worked for me.
You should be able to put in two memory sticks, but it's worth popping the back open to have a look first.
The harddrive is a good idea, but I recommend checking the drive speed. 7200RPM is recommended, but most harddrives are 5400 or even 4200. It makes a difference, particularly if your OS does lots of paging.
Your first step should be to search the net for the specs for you machine to make sure it is capable of supporting what you intend to put in it.