We are working on it at the moment, althogh i dont know if any one is activly working on it at the moment the chips are included in this message to a fourm member
the chip used in the c3k is the SHARP K4S561633F (256Mbit) in the BGA pakage while the replacment is a K4S511633F also in the BGA package, both are pin compatible with each other and meet the same timing requirements, the K4S51633F (512Mbit) however is a slighly diffrent package and may have to be chacked to see if it will fir (its slightly wider) however i dont see this being an issue. unfortunatly the 512Mbit chip is the highest capacity of the mobile sdram range
at the moment i am not persuing it as i cant remount BGA parts but if you sucsefully do it drop me a line as i want to get it done as well. my main goal at the moment is the VGA stuff and seeing if it is possible to do all the hacks mentioned in my post.
and you have to recompile a custom kernel to enable support for the extra ram
as for pics do a search in the hardware fourm for "pic" and "disassembly" as this should bring up the post you want, if you still cant find it look for topics where i have posted and you should see it pop up
the ram upgrade should work out of the box, and should follow the same procedure as the c7xx hack