Homebrew PCBs

Hello...

I looking to the DLP thread for E260 printer. I like idea but the E260 
is now hard to get here. So I look the web and found that someone has 
converted the Brother  HL2230 to DLP too. Neither that is available. But 
the Brother HL2130 is similar. So I already ordered that. I also get the 
service manual. I like to get some guidance how to convert it. I know 
that I need to somehow override switches, and to remove fuser unit. The 
paper path is near straight so there should some job to be done to be 
perfect straight, and to be room for thicker board. But what about 
-voltage in transfer roller? If I understand correctly the aluminum 
sheet is grounded but the transfer roller in HL2130 is in - potential.

Some guidance?!?

thanks.

Slavko.