The edition came out in 1998 and has long since disappeared from the shops; it can now only be had on the second-hand market. Prices there depend heavily on what happens to be available: around 2011, fountain pens from this edition were being asked about 1,100 euros, and whether such a figure is reasonable in a given case cannot be said in general terms. It is sensible to watch the market for a few weeks before committing. Only by comparing several listings — each with an eye to condition, completeness of box and papers, and nib width — do you get a sound feel for a realistic price level.
When it comes to changing the nib, caution is called for. Montblanc does not keep spare nibs for a 1998 edition indefinitely, and the nibs of the Writers Editions carry an engraving specific to the edition, so any ordinary Meisterstück nib cannot simply be fitted. Whether a change of nib width is still possible at all, and what it would cost, should therefore be established with Montblanc before buying. If you depend on a particular width, you are better off buying an example with the right nib from the outset.