I'm planning to cook a regular chicken on Sunday and I thought that I should probably try to season it somehow. I've never tried to cook a chicken before (first Christmas dinner as an adult obv!). I thought about stuffing it, but scooping out the stuffing after to eat seems a bit gross to me. Will the stuffing itself impart flavour to the chicken meat?
IMO you should only use herbs some onion and fresh fruit as others have stated. Anything that is bread based must heat to 160 to be safe to eat after the fact which means by that time your chicken will be likely 170 and dry. If you insist on a proper stuffing then pull your chicken at 160 then remove the stuffing and put it back in the oven till it's 160
The stuffing doesn't add much flavor to the chicken, so no.
If I even bother making stuffing, I like to cook the it in a separate pan. I usually have better luck getting the stuffing to a safe temperature without overcooking the meat, and it doesn't get as greasy. It also lets me get plenty of crispy brown bits on the top of the stuffing, which you really don't get if you cook it in a bird. I often use fat drained off of drippings from a previous roast chicken to cook the veg for the stuffing, and I use homemade, concentrated chicken stock (made from the carcasses of previous roast chickens), which I think gives the stuffing just as much chicken-y flavor as cooking it inside the chicken.
You can put other things into the bird to improve flavor if you're worried about it being bland. I like to season with salt and pepper inside and out. That's all you need if you have a really good chicken, but sometimes I'll cram half a lemon, half an onion, a couple cloves of garlic that I've bashed with the side of a knife to crack them open a bit, and some fresh herbs inside to play with the flavors.
This is an odd kind of answer to the question that you're not exactly asking;
If you're interested in stuffing the bird, and consuming the stuffing, but not interested in the yuck of unstuffing the thing, you could fill an improvised food-grade net (i.e. cheesecloth, muslin wort/hop bag, grain sock, etc) that would be permeable AND allow for you to remove the stuffing more easily.
In this way, you get all the benefits of the stuffing flavoring the bird, you get a side dish, and both the act of stuffing and unstuffing will leave your hands reasonably clean.
I'd cook the stuffing separately; much easier to get both to the ideal temperature that way. You do not want to serve overcooked chicken, and you must not serve undercooked chicken or undercooked stuffing exposed to raw chicken.
I'd suggest brining your chicken (in a brine containing herbs, garlic, onion). Keep in mind that most of the herb flavor will stay in the brine, only a small amount will migrate into the bird; that is, if you taste the brine (before adding the chicken, obviously), it should taste of way too much salt, and also way too much of whichever herbs you used.
If you're going to roast the chicken with high heat, you'll want to have little if any sugar in the brine. 5% or so salt (by weight vs. the water), maybe 1% sugar. Look up some chicken brine recipes to find some good flavor combinations.
Cool the brine before adding the chicken (easy way: make it double-strength, and dilute 50% by weight using ice). Brine for around 12 hours (in the fridge); rinse and dry the chicken as well as you can with paper towels; return to the fridge, uncovered, for an hour or so (to continue drying); then roast.
And, most importantly, do not overcook the chicken. The brining gives you some leeway here, the goal is 165°F for the breast and 175°F for the legs.
If you make gravy or pan sauce, the drippings from a brined bird will be fairly salty; don't add additional salt without tasting, use unsalted butter in the roux (and have some low-sodium chicken stock on hand should you need to dilute to reduce saltyness).
Note that the stuffing goes into the neck end, filling the flap of skin there, not the body cavity.
If you were to put stuffing into the body cavity, you would end up with a greasy, sloppy mess, and it would indeed be gross.
Stuff the neck end, and you're likely to find it more appetising than you're expecting.
The stuffing does impart some flavour to the meat, but it doesn't penetrate very far from where the stuffing is.
Stuffing does mean there's more mass to heat up, and impedes the transfer of heat into part of the chicken, so you need to take that into account when deciding how long to cook for.
I don't know what company you'll have, or how much emphasis your culture puts upon Christmas dinner -- but I think it's pretty bold to try anything for the first time on Christmas day. On that basis, I'd suggest making things as simple as possible, and that means not stuffing the chicken; try that another weekend.
Some form of stuffing is a Christmas dinner essential though. Use packet mix and cook it in a separate tray.