It depends which version of Windows 7 you want, as some have more services running than others. I think ReadyBoost should also be considered. If you consider the situation, that your laptop has used its 1GB of RAM and applications are still requesting more. Usually something called paging or swapping takes place, so basically your HDD is used instead of the RAM (Virtual Memory is used). This of course is MUCH slower and this is when the performance of your laptop will be reduced. Buy a fast (but not too expensive) 4GB memory stick and dedicate it to ReadyBoost (right-click on it in My Computer and you'll find it), and see how this affects the performance.
ReadyBoost isn't a replacement for more memory, but in this instance, i think it might be beneficial to you. ReadyBoost uses this flash media for swap space, as virtual memory, instead of the HDD, and of course that flash media is much faster.
By the way, I upgraded the RAM as soon as i got my Mini 10v, following a YouTube video, and i am quite risk averse and have massive hands etc etc, and i did it without issue.