Since when is 196k high mileage for an XJ?
Basically, I would just change all the fluids if you don't know the last time they were changed or if they are due. You may want to replace the belts and hoses depending on age and condition. Aside from that there's really nothing special necessary aside from normal maintenance. If you change the trans fluid (auto) make sure to use DexronIII/Mercon this is what the Aisin AW4 takes (the transfer case also uses this).
As for oil the 4.0L I6 isn't picky, it will run on just about anything that says "Motor Oil" on the bottle (5/10w30 or 5/10w40). That being said high-mileage oil can't hurt, Shell Rotella T5/T6 are also popular options which tend to perform well in the 4.0L. Just make sure to use a good filter (not Fram, STP, or an off-brand) Purolator (especially the PureOne), Mopar, Wix and NAPA Gold (rebranded WIX) are the preferred filters.