I have a 1998 with 151,000 miles on it. Replaced the head gaskets and valve body gasket at 132,000 and it has been going strong. However, with this age and mileage it seems too be eating through parts. I like my truck so I think it is worth it but I doubt it is economical especially if you don't need a truck. As far as replacing it with another ranger, you don't really know what you could be getting yourself into. I have so much parts and money into mine now if I got another truck I would likely have to replace those parts all over again.
If you just lost reverse it could be something stupid like a solenoid or valve body gasket. You could find new valve bodies with solenoids for fairly cheap. If this is the case it should be a lot cheaper than $1200.
98 XLT "Off Road" 4x4, Gutless 4.0 Automatic, 4.11 265/75/16, Supercab, SCT Tuned