Yes, it's possible.
No, you specifically (OP) should not attempt it.
Working with SMD and modern day components takes literally years of soldering
practice due to the size of the solder traces. Even something "sorta simple" like
replacing the memory chips with their upgraded brethren would be half a nightmare.
Even if you discount the soldering skill required the rows and columns probably
wouldn't match the rest of the hardware chipset so you probably couldn't access
the rest of the memory anyway. It just depends really, and serious research and
studying would be required to do any real upgrading.
Besides upgrading the system ram (256>512mb, say) there really isn't anything else
that would be a worthy hack. Well, ok, fine, there are three projects that might be
considered worthy I've seen so far.
1> The aforementioned heatsink mod. Decent.
2> Some guy is trying to get video out on the Droid, but it's not going real well.
3> Someone is trying (or even succeeded by now) to get the USB to function
as host mode letting you attach USB devices (book drives, keyboards, mice, etc)
directly to the Droid. Worthy hack, aye.
The rest of the hacks I know of are all done without opening the case. Linux,
overclocking, things done in certain ROMS, and so on.
TLDR: Don't open your Droid up, you aren't that skilled. Practically no one is;
and, you would already know *ahead* of time if you were that skilled & would
not have asked.
_smiles gently_
--Dietche