Hi SELfour50, the price certainly seems right, and there is every chance that if you fitted the gearbox "as is". that it will work satisfactorily. It becomes a matter of trusting the seller's description.
There are some things you can service and perform checks on which are inexpensive and relatively quick. Initially, I would remove the sump and valve body which can be cleaned in petrol and blown clean with compressed air.
You can also service the front pump by installation of a new oil seal and rubber 'O' ring, and check the adjiustment and clearance of the No. 3 band, which is the one closest to the front of the box. It partially controls operation of reverse. It is also possible to check free movement of Bands 2 and 1 (middle one) which should have free travel of 4mm, This measurement is obtained by means of compressed air inserted into orifices that are part of your servo units. However, to adjust the free travel of those bands it is necessary to remove the servo units and use different length adjustment pins.
With the front pump off, and the valve body still removed, you can wash out the box with petrol and let it drain out as best as possible. Once the front pump housing is refitted, you can also turn the box upside down and again expel all excess petrol.
Clutch packs and Bands can only be examined by further stripping of the box. Regards Styria