First off, congradulations
Other than the built-in messages Sedo lets you choose from (ie: sending custom message), Sedo reads and has to approve anything you put in that message-box. If you put that you'll keep the domain for a few years unless they come-up offering more money, Sedo staff likely to either remove domain or just tell you to change the listing to a set asking-price rather than "make offer". Either way, Sedo not likely to pass that message on to bidder, because they figure you shouldn't be listing it as "make offer" only to then approach potential buyers with such a comment after they do just that (make offer).
IF you unpark it, remember that Sedo's commission on any sale through them may go up. From Sedo:
"No minimum fee if the domain is parked with Sedo; only the flat 10% rate applies."
In the case the domain isn't parked with them, you'd pay $50 minimum, regardless of sales price. So a domain selling for less than $500, you'd still pay $50 if not parked with them.
As to content on the site to prevent TM issues, atleast you're wanting to play the game smart! If a potential TM question is border-line questionable, having it on a page simply saying it is for sale (like Sedo's parked pages) tends to go against you with all the ICANN dispute panels. Albiet not automatic, they consider this as having no legitimate use/interest in the name, one of the grounds to loose it. As to the person going after a trademark, they don't already hold, just to get the name, is usually in your favor later (especially if you can show this is just why they went applying for TM). And, you stated:
I am afraid that buyer will get trademark for that domain and eventually crap my site for free.
TM would cost them a few hundred, and going after domain through the ICANN panels would cost $1500+ on average. This is not counting their time and effort. Your question would be rather this domain would be worth all that to them.
No matter how you handle this ---
GOOD LUCK with the domain!
Bid was 60 dollar and now I could have nice ROI, because domain was handreged 3 month ago. I wasn't planed to sell that domain in next 3-5 year... 
DNKitchen.com and Chef Patrick ---> 
