Welcome to the forum and congratulations on on the new boat. Do you know which year it was constructed?
Regarding the centre board, do you have a copy of the manual? If not, it can be downloaded, the only thing I can't remember is whether it is the Jeanneau website under the older models section, or is it in the document repository of the forum. Some other members may come in with suggestions.
If all else fails, send me your email address in a PM rather than in the open section of the forum - look under Messages tab near the top of the page - and I will send you a PDFs copy that I downloaded some years ago when someone was asking about your model. (By coincidence, I nearly deleted it only last week as my iPad seems to be running out of room! But I hesitated. Must have known you were going to ask.). The manual has a picture that is as they say in the classics, better than a thousand words.
Also look under hints and tips, there is an article on removing the centreboard of my SO30i which has many similarities in overall principal, though a slightly different system. I have some more to add to that as I had my centreboard out again only last week - went back in the water Friday, so it is all fresh on my mind.
In the high chamber or lifting box under the table, there is a fixed block and a fixed eyebolt right at the top. The lift rope goes over the fixed block, down to a moving block from which hangs the board. The board seems to hang on a strop or bar so the moving block is normally clear of the water, especially when the board is raised. Have a look at what access openings you may have, look for that manual then come back and tell us more about the issue that is worrying you. It is all easier when you have the picture.
The Sunway2500 looks like a lovely craft, you will get a lot of pleasure from it. (By the way I just noticed your heading to the thread again - I assume we are talking about the same model - the manual I have is for a Sunway, but even if it is a different model, there will be similarities so a reasonable place to start.
I had a look at the manual Malcolm provided the link for, thanks, Malcolm. It is a slightly different model from the manual I have, but the drawing in that Sun2500 manual is almost exactly the same system as my 2009 model SO30i, so the centreboard mechanism looks very familiar.