This is the guide I used. Read everything first.
http://discussions.nokia.com/t5/Pool...ata/m-p/591877

These are the 3 files you will need to get from the webpage.
a) maemo_flasher-3.5_2.5.2.2.exe
b) RX-51_2009SE_10.2010.13-2.VANILLA_PR_EMMC_MR0_ARM.bin
c) RX-51_2009SE_20.2010.36-2_PR_COMBINED_MR0_ARM.bin

Then once you have done that and you're phone is working, there is a nokia update, get that thru the app manager, then goto maemo.org and find and install CSSU Stable version.

Any further questions just message me as this is a differen't topic.