I've done it a few times and it's really not difficult

Usually the tricky bit is getting the back off. Google your model and "tear down" and there'll probably be a video that someone has done that shows where all the screws are on the back. Or the manual probably shows where the screws are. Usually the screws on the back are visible but sometimes there are a couple under one of the feet.
So it's
1) Take the screws out
2) You need something like a guitar pick to slide in the gap between the base and top to prise it open - can take a bit of time and patience. Slide it all the way round and you'll hear clips unclicking. Then take the back off - you might need to wiggle it a bit if some inner clips are still attached. I was quite nervous the first time I did this on a "thin" laptop but the back always goes back on ok and you have the screws (put the screws in a safe place!).
3) Once the back is off, put your antistatic wrist band on (before I had one of those I put rubber soled shoes on and leaned against a radiator (ie something metal - which grounds you instead). This is to avoid static.
4) Unscrew the screws holding the battery in. The battery is obvious - it's a big black slab!
5) Take the battery out
6) Next thing is take the ssd out - it looks like this
7) If you see that little semi circle on the left of that photo - that is where the screw is holding the ssd in. Unscrew that little screw - put it somewhere safe.
8) The M2 nvme ssd will then just pop up a bit at an angle (or you may need to lift it up). Then just pull it out of its connector.
9) Put the new nvme ssd in the connector. If there is a heat pad attached to the old nvme, peel that off and stick it to the underside of the new one first.
10) Ensure the nvme is pushed right into the connector, then put the little screw back to hold it down.
11) Put the battery back in (slide it into its connector) and then put all the battery screws back in
12) Press the back back on the computer - put all the screws back in.
Done.
It's a 5 minute job at most. The main thing is to earth yourself so you don't create any static - the rest is just taking a few screws out basically.
I've done it at times where I forgot to take the battery out first (not recommended) and it was still fine.
Once you've done it a few times it's easy
I can understand nerves over it with a brand new computer though.
There's an HP video here for your model that visually shows how to replace things in your computer and shows how to take the back off. You just need a philips screwdriver with the right size head for the screws - and a guitar pick or similar (they use a plastic pry tool). And an antistatic wrist band. The screws are all visible on the back.
At 5.00 in the video it shows how to replace the nvme ssd. You also have upgradeable ram - which is good! So you can upgrade the ram at the same time if you want.
Antistatic wrist band £4.99
If you don't have a guitar pick, I have one of these - very useful. I use the blue triangles for taking the back off (but there are also pry tools in the pack). It's worth buying for future use!
ifixit prying and opening tools £8.99