Tran / Diff oil change and other Q's

Hey all, I keep coming back to the forums for everything I need to know, its a fantastic resource. Thanks to all who contribute.
There are a few things I haven't seen a definitive answer on so thought I would ask. (Please let me know if any links cant be posted and I will remove them)

I picked up the Jimny 2003 in August at around 63k miles, and its now around 77k. I serviced at 64k and again at 73k and am due for a transfer and gear box oil change (according to the manual, and my sanity). I do a lot of miles sadly, and its mostly motorway.

I already purchased the oils for this back in Nov, but think one may be wrong after seeing an old post on here today
TRIPLE QX EP 75w90 Transmission Fluid Fully Syn
TRIPLE QX EP 80w90 Transmission Fluid 5 Litre

The 75w90 is "API GL-4 & 5" and read today that this should be changed to GL-4 only. Is this the case, or is the above right?

The other big question is around the sealant "Sealant 99000–31260 (SUZUKI Bond No.1217G)", everyone just says use sealant, but which one is right? Is Loctite 542 Hydraulic Thread Sealant right or is there something better?

I am a big fan of replacing the bolts and plugs as you go, since the Jimny has a lot of rust underneath I want to replace important plugs and bolts when I take them out and wondered if its possible to buy replacement plugs for this change? I replaced the sump plug with a magnetic one as this is always the first change I make on a car... nothing worse than having an old rusted plug you cant get out that just crumbles when you try.

The other bits I need to do in this service is replace the Accessory Drive belt, I can see that it does have some cracking occurring so want to get that swapped out. By the looks of things its a pain to get off and out, is this the case or am I over thinking this. It looks like pulling the RAD out is the way to get at it properly but that cant be right. I do want to replace the rad this year, but the latter part as it still works but it is damaged from stones. But no leaks and coolant is pristine (was when I got it).

Lastly, the car has central locking and I want to install a remote for this. I have the parts, and seen all the posts about it but where is the wiring for this located? I am gathering its under the steering wheel?

One of the rubber mounts for the exhaust broke this week so have to get that replaced as soon as the replacement arrives hoping its not too bad of a job, its the one in the center of the car.

Sorry for the long post, and thanks in advance for the help.

Yes you need GL4 for the transmission rather than a GL4-5.

What's the sealant for? I've never needed any for servicing but if I did I'd use the same tube of stuff I use on everything else rather than anything specific.

Yes you can do the belts without removing the radiator. It's helpful to look up a picture of the power steering tensioner so you know where to put the allen key in to tension it up again. There is also an 8mm allen key bolt at the bottom of the alternator that works as the pivot. This normally needs to be slackened and access is not ideal but perfectly do-able. Saves 40 minutes draining, removing, refitting and refilling the radiator!

Thanks Busta, I will have to see if they will swap the oil out for me. I doubt it as I bought it back in November. Guess it will have to go on eBay if they say no.

The Sealant is mentioned in the manual for the drain plugs. I have seen it mentioned on the posts on here too, but nothing specific to go and buy. I dont have anything at home so will need to buy something for it.

EDIT: They may actually replace it, but they dont stock anything that is GL-4 and 75w90 (and reasonably priced).
Its either the 80w-90 or a 75w90 that is more than double the price. manual does say 80w is fine, but 75w is preferred.

Hylomar blue is the sealant I normally use.

Regarding the oil grades, what year is the manual from? If it's post 2005, ignore the 'preferred' oil bit. The newer gearboxes have some issues and i believe Suzuki recommended thinner oil as a fix, but this doesn't apply to the normally bulletproof early gearboxes.

Thanks again, I will look for that same Sealant, use something people have used before

Its a 2003