One more they have a white 98 discovery with 98k on it seemingly NO issues Im tempted to offer 3800$ This is the lowest mileage I have seen so far, does this seem decent?

If it indeed does not have any major issue I would say that is closer to a good deal for you given your feelings about the XD. Maybe somebody else will chime in and give you some better feedback than I can. But 98K on a 98 is pretty good IMO. BTW I would rather buy mine from an individual rather than a dealer as they are trying to make 1 or 2k on a LR you could get from an individual for 2 or 3K instead of 3,4,5K. You get the point. Whether you buy from a dealer or an individual you will still run into the same infamous LR issues that float around so keep that in mind. And you will still need to spend the money to do the 60K Maintenance posted on the stickie in this thread. You can save yourself some money with an individual buy from someone that is just not a Landie at heart and can't handle the TLC required or doesn't like the gas mileage. Just my $.02

$4k is too high. I did a search for a DI for some time. I got one that needs head gaskets for $1500 but I figured if they were done already, any Disco would need them soon.

My rig has 94k on it and should be nice with a few hundred into it. I am doing the head gaskets myself though. As said previously - they are all broken. Count on having to do work to it. If you can't wrench yourself, this will be costly.

No hurry - that thing isn't going anywhere for $4k. I know you are anxious but chill - look what options it has. I wanted a grill guard and got one on mine. That is $500 I saved by finding the right one. Cruise craigslist daily and learn the market. No one wants these things and the price is reflected. Best of luck.

Buy the '98 with under 100k on it.

And dont rush just to get into one, that is always a huge mistake.
Take your time and let the right truck find you.