1994 Chevy 2 door tahoe/ full size blazer 6.5L Diesel

[Jeep_Comanche17]

So my aunt has a 94 Chevy full size Blazer with the 6.5L turbo Diesel, it is a 4X4 with an automatic transmission (4L80e). I know that these blazers are hard to find with the Diesel, it has less than 150K, and runs great. drives well, straight and shifts smooth, 4X4 works as well. body in good shape. My question is whats the value of the truck? my dad is thinking about buying it from her, and he wants to make her a reasonable offer. Thanks, Jim