Firstly, the 165C and 180C are the only Powerbooks of that generation with a color screen. I don't know if it is swappable with a black and white LCD, so I'll let that one pass as a possibility. It may also be possible someone used the plastic from a 150 to repair a color screen model.

I have to call you out on the PPC upgrade, though. There was never any PPC upgrade available for 150 Powerbook EVER. What you very well may have is a 190cs, which is more like a 5300 than a 1xx series, with PPC upgrade. That is the lowest model number with a color screen that can be upgraded that way.

Also, 1xx series batteries are VERY easy to find with a Google search. They are NOT impossible to replace. Here is the main battery for $23.99

http://www.diversifiedbattery.com/powerbookmac170nicd.html

And the CMOS battery for $14.95

http://www.ebatts.com/apple_powerbook-150_laptop_cmos-batteries_part_b-40060f.aspx?GCID=C10847x023&KEYWORD=Apple%20Powerbook%20150%20Computer%20CMOS%

If it's a 190 you have, those batteries are equally easy to find.