Hello,
I am so new to this whole thing that I didn't even know one could sell a domain to someone else.

I have a name I registered years ago for an idea I had. I havent had a chance to develop a site for it, as we have another group we mainly work in. There is no site for it.

Now, I just got an unsolicited certified offer for my .com domain for $1500 via my ISP (network solutions). I responded that I would sell it for $10,000 (hey, what the heck, right). Then I recieved a private email from the guy saying his 'client' didnt have $10,000 but he did have $5000 and would I sell it. I ignored the email. The 7 day offer period passed, and he didnt go for it (it lapsed). The very same day, I recieved another certified offer for $10,000. ($10,000 is the maximum Network Solutions lets you ask for.

Now, the question is: should I just go ahead and sell it? I mean, maybe its one of those domains worth oodles? How would I know? Maybe he's the only one who wants it, maybe tons of people want it.. I dunno. I also own the same domain as a .us (which sounds really cool).
The .org and the .net are owned by someone else who appears to be taking offers, but when I inquired I did not receive a reply.

I did the network solutions domain appraisal and it came up for around $1800 (which was no help).

I have 5 days to figure out what to do.
I am involved in humanitarian work so $10,000 will be of great help... Simultaneously, I don't want to be stupid, more $ would go even further.
Its a gamble if I hold on to it.. is it a gamble if I sell.

Any advice would be most greatly appreciated. The sooner the better

With thanks,
Bard

PS I will provide the domain name offlist, but prefer not to list it here.

Well without knowing the domain name itself no one here acn help you. It may be a gems or it may be a junk. It fully depends on the domain name itself. Please try and list it here you might get more oofer then the guy who is offering you the amount.