well done!

first thing I always do with a new one is change all the fluids,
everything. though I'm not sure about the swivels and one-shot, if it
has some in then great, I suppose you can tell by opening the drain
plug, if you get wet it's ep 90, if it's thicker like runny grease
then it's one-shot then put the drain plug back in sharpish.

Difflock.com do some interesting synthetic (I think) gear oils longer
life/quieter running etc, not tried any myself.

Oil treatments, some people swear by them, some people swear about
them. but most people agree that you should use something high quality
(SPI etc) and the correct viscosity as in the manual I use millers
oils myself for engines.

Fuel treatment, a good dose of injector cleaner annualy is a good idea
in my opinion.

oil, fuel and air filters too.

Also change the cam belt if you can't be sure when that was done and
the aux belts too if they look at all worn (might as well eh).

check the levels of the battery. tyre pressures, bulbs (I always fit
osram silver star headlamp bulbs).

I'd fill-up with diesel and a heavy heavy dose of injector cleaner and
take it for a good hard drive.]

As for chassis treatment, you could go for waxoyl but I'd have it done
by someone who knows their stuff, my new disco (10 year old ish) will
likely be going to see www.before-n-after.co.uk for their waxoyl
treatment (it's a pain in the arse job and I'd rather pay my money and
have a pro do it properly).

Get yourself a Haynes Manual and if you can find one a LR owners
workshop manual, they'll tell you all you need to know, most notably
how much of what kind of fluids go where and when. (amazon/ebay).
There may be some info for you on one of my websites www.4x4info.info

spare wheel carriers:
a review of 6 in LRO magazine rated the Mantec 2-SA50/A (£214.67) and
the Scorpion Racing RWCHL (£205.62) as the best of the bunch (the
latter also has bits for mounting a hi-lift jack).
I've never tried nor used either myself.

Regards.
Mark.

Check if it needs a Cam belt modification to  prevent early failure of the
belt; personally I'd change the belt as a matter of course anyway  ~ £ 200
indipendant if you don't do it yourself. All round pads check, fluids change
as a matter of course ( axles, diff, gearbox etc.  ? not sure of this for
yours depends on use and abuse before ). Use best spec fluids, make sure you
get correct tyre pressure for oddball size tyres.

Millers oils and diesel additive.