Before I say anything else: Whoa, that's an interesting computer. Pretty cool.
Anyway... about the mods. (I'm just searching around on the internet, if it wasn't already obvious; I have no experience with Eee hardware.)
- This link is a wiki of Eee PC upgrades, such as hacking a USB flash drive in as storage, but that takes serious hardware modding skills
- this blog article says it's sometimes possible to replace the wireless card with an ssd (I think?)
- This EeeUser Forums thread is the best info I've found so far; it looks like the 4Gb SSD is soldered on to the motherboard (and therefore not upgradeable), however some(?) of the shipped models have a mini-PCI slot that can support an SSD with hacking, and more importantly it's relatively easy to put an sd card in and boot from it.
Since there's such a large group of Eee PC enthusiasts (apparently), I think your best bet is to join a forum where people have hardware expertise with your system, and ask them for advice.