can buy and upgrade yourself. go SLS buy the laptop RAM. there's a hatch(or whatever) underneath youyr laptop u can open to add the RAM. check your manual and also see if you have spare slots, if not you may have to buy more RAM. eg 256mb to replace 128mb instead of adding on 128mb.
actaully you can upgrade your HDD, RAM, CPU for ypur laptop the rest are pretty much stuck to the mainboard. Howevery it may not always be the case,
e.g RAM: you may have onli be able to upgrade to 256 MAX if you happen to have 2 RAM slots as some mainboard support onli 128MB per slot. it generally depends on the baord. mine is stuck @ max 192 (64MB fixed)
For CPU, not every laptop allows you to do so, its also more tricky as mobile laptop processor is not readily avaliable as comapred to normal desktop ones. I think if you're not too sure about it, get seomone who is more technically inclined.
finally for HDD, ususaly you can upgrade it easily, cos mose HDD are quite accessible. You can get it off the shelves easily too. However ples note that not all HDD works with the laptops. Especially if you have those ultra portables, chances are you need to have HDD that is of 9.5mm in heigh. Some higher cap HDD may go more than 9.5mm.