Installation should be straight forward - unscrew the cable, screw in the sensor.
Not sure if you're interested, or if you already have the sender, but there are much more cost effective options. I just used one from a mid 90's R150F V6 4runner, $4 from the salvage yard. It has a 11/33 driven gear on it though from the 4.10:1 gears. I'm researching the part numbers for the other driven gears. Many other cars use the same sensor:
Lexus LX470 1998-2004 V8-4663cc 4.7L Vin 2UZFE
Toyota 4 Runner 1992-1995 V6-2958cc 3.0L Vin 3VZE
Toyota 4 Runner 1992-1995 L4-2367cc 2.4L Vin 22RE
Toyota 4 Runner 1996-2000 L4-2693cc 2.7L Vin 3RZFE
Toyota 4 Runner 1996-2000 V6-3378cc 3.4L Vin 5VZFE
Toyota Camry 1994 V6-2995cc 3.0L Vin 1MZFE
Toyota Camry SE 1994 V6-2995cc 3.0L Vin 1MZFE
Toyota Celica 1994-2001 L4-1762cc 1.8L VINS 7AFE, 2ZZGE, & 1ZZFE
Toyota Celica GT 2002 L4-1762cc 1.8L Vin 1ZZFE
Toyota Celica GTS 2002-2003 L4-1762cc 1.8L Vin 2ZZGE
Toyota Corolla 1993-1997 L4-1762cc 1.8L Vin 7AFE
Toyota Corolla 1993-1997 L4-1587cc 1.6L Vin 4AFE
Toyota Corolla 1998-2003 L4-1762cc 1.8L Vin 1ZZFE
Toyota Corolla (CAN) 1993 L4-1762cc 1.8L VIN A
Toyota Corolla (FWD) 1992 L4-1587cc 1.6L Vin 4AFE
Toyota Corolla All-Trac 1992 L4-1587cc 1.6L Vin 4AFE
Toyota Echo 2000-2003 L4-1497cc 1.5L Vin 1NZFE
Toyota Landcruiser 1998 V8-4663cc 4.7L Vin T
Toyota Landcruiser 1999-2003 V8-4663cc 4.7L Vin 2UZFE
Toyota Matrix 2003 L4-1762cc 1.8L Vins 2ZZGE & 1ZZFE
Toyota Pickup 1992-1995 V6-2958cc 3.0L Vin 3VZE
Toyota Pickup 1992-1995 L4-2367cc 2.4L Vin 22RE
Toyota Pickup T100 1993 V6-2958cc 3.0L Vin 3VZE
Toyota Pickup Tacoma 1998-2001 V6-3378cc 3.4L Vin 5VZFE
Toyota Pickup Tacoma 1998-2001 L4-2438cc 2.4L Vin 2RZFE
Toyota Pickup Tundra 2000-2003 V8-4663cc 4.7L Vin 2UZFE
Toyota Pickup Tundra 2000-2003 V6-3378cc 3.4L Vin 5VZFE
Toyota Rav 4 1996-2000 L4-1998cc 2.0L Vin 3SFE
Toyota Sequoia 2001-2003 V8-4663cc 4.7L Vin 2UZFE
There are lots of used and aftermarket on eBay for cheap. The driven gears will likely be incorrect though.
Also, the Previa has a mechanical->electrical adapter from the factory, same function as the Marlin one.
