Since the previous posts are old, I thought I might take up the torch a bit.
According to the specs I have found, the system is, hardware wise, very similar to some models of Compaq Presario C500 and I have a decent bit of experience with that.
The NW8440 SEEMS to be blessed with the higher end 945 north bridge from the start, though you may want to try and make a visual inspection of that if you can.
Assuming it is, 4 GB will work. The second RAM slot is under the keyboard, similar to some models of Dell Latitude and Precision from around the same time frame as the NW8440. If you're not positive about how to safely access it, here's the HP maintenance manual from their site for that model:
You should be aware that it is possible that even if you install 4 GB, only 3.25 GB of it will be "usable." This was found to be the case in the tests we ran in another thread for the C500, and I know it's also true of my boss's Dell Precision M65 which has the same north bridge.
Still, 3.25 GB is better than 2 GB.
As far as the SSD: Assuming that the hard drive interface is SATA and that you can run it in AHCI mode (check the BIOS for the settings, it may be listed as SATA Native Mode On/Off or similar. ON would be AHCI, unless I'm mistaken), an SSD would be a nice upgrade. There is no reason I can think of that it wouldn't work, as long as the above two points are kept in mind.
If you want to be brave, depending on what CPU your model is equipped with, you could also try your hand at upgrading that. That's entirely up to you, however, I just thought I'd throw it out there.
Hope that information helps you out some!
O Shadow Fox O