Bridgeport BOSS

I have recently purchased a Series I Boss. I need to replace the
spindle ballscrew. Where can I find an affordable replacement? I
have also been reading about some low cost conversions. With this
being my first adventure in CNC retrofit I would like to get some
additional information on this particluar conversion and even some
basic information about matching steppers, power supplies, drivers,
and software.

Thanks

Scott Hamilton