I know there is software to do it, but I'm likely 15 years out of date. I know it was call Norton Ghost. Not sure if there is any open source or cheaper alternatives these days. I know I tried a rather simple search a few months ago and just went "fuck it" and did it the hard way

I regularly use these sorts of programs, as I clone my computers' drives each week. With Windows, I use a program called Partition Wizard (a freeware edition is available), and for Linux (or when using a live CD), I use DDRescue.

I recommend Clonezilla, it's good especially if you're replacing a drive which contains an OS.

I agree with the above about clonezille. It's a good free tool I know of for this. That's not to say there might not be better ones these days, but when I've had occasion to do this, clonezilla is what I've used. I've heard good things about Macrium Reflect and I believe it might have a more friendly interface, but I have never used it.
Keep in mind as well, you may need to do some stuff in your BIOS to tell it to boot to the new disk, as it will probably be looking for the old one.

what if the PC only has 1 HD?

In that case there's a good chance it will default to the new drive, but it might just go 'oh the thing i had before is no longer attached, I'm gonna go to the boot menu, or I'm gonna try and boot to optical or usb and give an error'.
I'd hope into my bios ahead of time and just familiarize myself with the boot setup just in case. Even if you arent comfortable messing around in bios hopping in there at boot and looking around is nbd, just don't make changes or hit save or anything. That'll let you know what it looks like now in case you have to go back in later.

If you do have to make a change, it should be as simple as saying, hey the boot order now has this drive first, or include this drive in the boot order. It's usually pretty self explanatory

changing the BIOS gives me anxiety. that's why i've never done a BIOS update.

Yeah I understand that feeling lol and I work with computers every day. Somehow when it's your own box though it's more stressful especially if it's your only pc. I am typically to lazy to do bios updates except at build anyway.

So if you have to do anything at all here, it should be really simple. I'd go in now find the section with the boot order and just look at what's there so you know what it looks like. Its often worth it to take a picture of the screen with your phone in order to document the existing settings to reference later (if it's anything complicated). Then I'd clone my drive, un-hook the old one (noting what data port its physically plugged in to just in case, or you could probably just unhook power and leave data plugged in) plug in the new one and see if it boots. If not I'd go into bios and see what available boot devices there are and pick the new drive as primary if its not already, making very sure I knew exactly what changes I made. Then save and see if you boot. If you are careful to know exactly what it is set to prior to any changes, you can always set them back how they were, just hook the old drive back up and get back to square one if you have to. It's also normally a good idea to only change one thing at a time so you know if what you did is working, but in this case you should only really be changing one thing (unless maybe your new drive defaults in bios to the wrong mode or something, but that is unlikely).

Oh also its important when you clone to clone the entire disk, all partitions in the same order. You need to keep the little system reserve one at the beginning of the disk and like the recovery one at the end. This will happen automatically if the tool you use clones the entire disk, but if it asks you to pick partitions, do all the ones from the original disk and put them in the same order on the new one.

hmmm. feeling emboldened now. think I'll give the laptop a RAM upgrade while I'm at it.