Just wondering what your thoughts are regarding spark plug replacement. 2009 4.2 SC with 101000 miles. I've owned it three weeks but with all the craziness, only driven about 450 miles, most of which were on the highway bringing it home. Starts, idles, and runs smooth. Gets reasonable (for a RR) mileage, has good pickup. Basically I have no reason except the odometer to change the plugs. So should I do it now or wait until there's an issue?

Follow up: if I do change them, what other updates should I get along the way while I have everything apart?

OK, first port of call is the service history [assuming it has any?] If it's had plugs in the past 50k then they're probably ok. If there's no history of plug change and/or oils & filters then I personally would start from scratch & do everything in a reasonable time frame. 100k on original plugs is pushing the realms of reliability a bit too far, they would have been changed at some point......surely?
Obviously start with engine oil & filter along with air filter[s] & fuel filter if applicable [I'm a derv man so unsure if these SC's have a fuel filter] & of course a set of decent plugs. Follow this with drive train fluids........Then enjoy..........  2012 Orkney Grey Westminster 4.4TDV8 with Ivory interior.........nice!
BMW R1200GS
Alfa Romeo Giulietta
Just one Montesa now, 349 White Wonder
Austin A40 Farina MK2
1975 Morris Marina 1.8TC

With ANY car I purchase, it gets a full service. All filters, and plugs if a petrol car. At least then, you know where you stand with things

I give the same advice to my customers too, unless there is a documented history

That's pretty much where I'm at as well. I have the carfax, but it isn't a complete history. Engine oil looks fine for now, as does brake and power steering fluid. I blew out the air filters just for grins but they were clean, too. I did coolant flush, transfer case, and transmission fluid over the last two weeks. Waiting on a fill plug and fluid for the differential(s) change, but should knock that out this weekend. That leaves..... Plugs and fuel filter? Suppose I should figure out where the fuel filter is and how to change it.

Thanks, guys! 2009 L322 SC

Being slightly OCD in the oil department, if that were mine, I would drop the oil & filter for two reasons 1) no idea who’s oil is in there & how long and 2) piece of mind that ‘my preference’ of oil is in there. Oil is not expensive compared to what you paid for the car so do the RR a favour & drop the oil. Oh......while you’ve got your head under the bonnet change the plugs!😂😂 2012 Orkney Grey Westminster 4.4TDV8 with Ivory interior.........nice!
BMW R1200GS
Alfa Romeo Giulietta
Just one Montesa now, 349 White Wonder
Austin A40 Farina MK2
1975 Morris Marina 1.8TC

If I recall correctly, Land Rover recommend that the spark plugs are changed at 105,000 miles under "normal " driving conditions. The fuel filter is part of the fuel pump in the tank.

Fox889, I agree with you on the engine oil change. Just put it off in terms of priorities. I can look at the engine oil and make some determinations as to the wear it has endured. I can't easily do that for any of the other oils, so they went first. There are brake fluid, and coolant flushes periodically on the Carfax, which is good. I didn't see any reason to think that ATF or differentials had ever been touched, but luckily there was no metal on the magnets on the ATF pan, and the transfer case oil didn't look terrible. But as others have said, better to change them so you can be sure. Shopping for plugs and a fuel filter now....It's only money, right?  2009 L322 SC

It is 'only money'.............it's just that you'll need plenty of it with a FFRR 😝  2012 Orkney Grey Westminster 4.4TDV8 with Ivory interior.........nice!
BMW R1200GS
Alfa Romeo Giulietta
Just one Montesa now, 349 White Wonder
Austin A40 Farina MK2
1975 Morris Marina 1.8TC

Thanks for the advice, Gents! I changed out the plugs this afternoon and then took it for a 50 mile drive on the highway to make sure everything was working properly. Got 18 mpg at 80 mph on a 50 mile loop. The only reference I have is that the day I brought it home I got 15.1 mpg at the same speed on similar terrain and similar wind conditions. Is that possible that I got a 20% improvement in fuel economy from just the plugs? I can't imagine changing all the drive train fluids made much difference in mpg. 2009 L322 SC

You blew out the air filters + new plugs......all adds up to a more efficient engine I would say.
Happy Days. 2012 Orkney Grey Westminster 4.4TDV8 with Ivory interior.........nice!
BMW R1200GS
Alfa Romeo Giulietta
Just one Montesa now, 349 White Wonder
Austin A40 Farina MK2
1975 Morris Marina 1.8TC

In case anyone was wondering what a 101K mile spark plug looks like. I'll never wait that long on any vehicle again. It cost $60 and took about 1.5 hours start to finish.

Click image to enlarge

Holy Toledo! That's a worn plug for sure.
Now you can see why I & others say 'new car, blank canvas'.
You can now pat yourself on the back & say another box ticked!
Well done chap. 2012 Orkney Grey Westminster 4.4TDV8 with Ivory interior.........nice!
BMW R1200GS
Alfa Romeo Giulietta
Just one Montesa now, 349 White Wonder
Austin A40 Farina MK2
1975 Morris Marina 1.8TC