Didnt you check oil level a week ago when had oil changed,? That's what you are supposed to do, specially if someone else is doing oil change, then you would have known if it's loosing a quart a week or simply wasn't filled to correct level,
Never assume any oil change Place will do a perfect job, always double check yourself, also always check tightness of filter & drain plug when someone else is changing oil for you, so many times they will forget to tighten either or both,

 

I didn't check the oil level last week because the previous owner said he had just had it changed. I naturally assumed that it was done correctly, but I've never cared for a car as much as I have this one so I've never had a reason to think it wasn't done correctly.

I will check filter and drain plug today. I'm also going to the car wash and cleaning underneath so I can track the leak(s) better. There's so much dirt and oily "mud" underneath there's no way I could track a leak right now.

 

After 100K everything is leaking/weeping/dripping on a Disco2. Not to mention all of the parts that start going out. And the engine probably runs hot as radiator & heater matrix begin to plug, viscous fan loses its resistance, the head gaskets are letting coolant & exhaust gas go by. It's a living nightmare all I can do is wish you luck & advise you to keep tabs on the engine coolant temp with anything other than the dash cluster. Whenever that gauge shows the engine getting hot its way overheated by that point. Some others will make suggestions but I started off using my OBD reader to watch coolant temps & then installed a gauge that displays the coolant temp in real time numbers. You can just skim through the first couple pages under D2 subforum and find a half-dozen posts on oil & coolant leaks, where to start looking for them, & so on.

In your spare time log in to the site & do forum search for whatever topic you wish or problem that you are seeking to address & you will EASILY get anywhere to several threads to several PAGES of threads on the info which you are seeking. I rarely ever had to post questions as everything has been covered dozens of times and is all in the archive for your viewing pleasure.