Pictures are worth a thousand words.
The Turks did work on the 88s they received, some were converted to closely resemble their 1903 pattern mausers while others were almost left in their original German trim. You generally find most of them fall in the area between in terms of partial conversions and re-works (re blue, parts swapping..etc).
Prices I have seen vary greatly from $200 up to $400 for very clean, matching ones. I presently have 16 of these rifles and they are wonderfully well made considering the Germans were making close to 400 of these a day in 1890-91.