ackRite, most removable notebook optical drives that come in standard 12.7mm height
interchangeable. Just remove the drive from your notebook's custom caddy and replace it with the model you wish. Keep in mind that most aftermarket optical drives come with a simple black bezel that may not match your laptop's color scheme/shape. Bezels themselves aren't usually interchangeable, but sometimes a brand will use the same bezel fitting for different models (ie. Teac DV-W22E and the newer Teac DV-W24E). I just performed the above upgrade and now have a 4X DVD+
RW in my laptop.
Most new notebooks with integrated wifi conform to the miniPCI standard. However, some manufacturers (like IBM) BIOS-lock their notebooks so that they only accept certain miniPCI wifi cards. Installing an unsupported card in these BIOS-locked machines will simply fail to work, check first.
As for Dothan Pentium M upgrades, search for the following retail "boxed" codes (1.7, 1.8, 2.0, respectively):
Froogle returns a number of listings, but none are in stock as of this post.