I have used an M800 for decades with its colorhead. The M700 is its predecessor, and after all of these years, I still do not know what the difference is. All of the accessories and parts seem interchangeable. I also have a B&W condenser version of the M700, a "good deal" purchase made years ago but not used. As for yours, the wear part is the projection light bulb, which may be getting hard to find in Europe, so I'd find and buy a couple for safe keeping. What distinguishes the M700/800 from later medium format Durst enlargers is that they are assembled from die cast parts in critical areas and almost never require any alignment or adjustment to functions. The later models are not as heavily built, but their colorheads are better laid out.
The weak part, and should be checked before purchase, is the two toothed tracks on the back of the head height adjustment column. These parts were made out of some sort of nylon, which has become brittle over time. People who try to fast crank that head up the column can break off teeth in the track, causing the height adjustment system to fail. In the day, Durst sold replacement tracks, easily installed, but that supply is gone. I few years ago, I noticed that new replacements were being offered by someone 3-D printing them, but it's a risk of doing business with old machines if you need and cannot find.
One tip for VC B&W printing: These older Durst colorheads do not have the range of color correction that later models have. I guess that the VC paper available 40+ years ago didn't have as wide a contrast adjustment as today's paper. So, to cover the very high and low contrast possibilities of today's paper, even if not regularly required, lay in some color filters to over the extremes. The enlarger has a filter drawer below the colorhead, so they are easy to use when needed.
If you use the colorhead for VC or color printing, note that you will need different diffusion boxes below the colorhead and above the negative carrier. These are designed to cover 35mm, 6x6, and 6x9cm formats. They used to be less available and fairly expensive, however it looks on ebay like the dealers are clearing out parts and accessories for these old enlarges right now. Availability is good, and prices are low. Buy what you think you may need but do not have, before they are gone.