Well, don't escalate unless you have to, of course. Support techs will immediately hate you if you're the type of person that screams you want the manager as soon as you walk in the figurative door. Actually I think that holds true most places...Karen at the coffee shop and all that.
I wanted to apologize as well because I think my initial message may have contained too much...umm...hope. I'm sorry if this is the case. The warranty (honestly) will not apply here unfortunately as the damage was not due to a performance or manufacture defect. You won't convince any technician that you need those three parts because the problem came from the laptop itself. You just can't make up a story for that. Well, you can, and I've heard some amazing fibs...but yeah. Explain the circumstances, perhaps you'll encounter a sympathetic tech. I would at least make a small effort as it won't hurt you asking politely if there's anything that they can help out with as they may be able to help as a goodwill gesture. If you do escalate you might be able to nag them (POLITELY) to where they will help you with parts because it's cheaper than continuing to deal with you...or they may slam the door in your face because of obvious damage. Escalate politely if needed, ask if it would be possible to speak to a manager about the situation, sound apologetic while you do so (any frontline tech takes as much or more abuse as, well, anyone in the service industry...be kind).
If you end up having to get the parts, then here are the factors to take into consideration:
1) If the keyboard is plasti-welded to the top plastic assembly, you will have to buy either the entire assembly from Dell's spare parts or be lucky enough to find it on an auction site. Unless you happen to have the plastic welding/melting gear and material which would be impressive. Either way, it's usually cheaper from auction sites if you can find the top piece and keyboard together anyway. Just make sure you get the regionally-appropriate keyboard for you (there's plenty of Spanish keyboards on ebay, for example, so be careful if you want a US keyboard instead, etc.) Example of US keyboard assembly with palmrest found:
2) Auction site or local computer recycling place will be the cheapest place to get the bottom piece and power plug. Examples:
3) Compare pictures against the parts you have to verify they're the right ones, and part numbers if possible.
4) Sometimes sellers will overcharge on the power plugs because it's a common breakage point. Compare with Dell spare parts.
5) From what I can see you're looking at maybe $80 to $100 of parts on the high end based on those examples? Replacing the laptop is around $550. Replacing just the plug will be cheaper if you're ok with the laptop appearing like it saved you from a bullet.
6) Dell's service manual will help somewhat with disassembly/assembly here: https://topics-cdn.dell.com/pdf/g-series-15-3579-laptop_service-manual_en-us.pdf
7) Mismatch your top and bottom replacement parts' colors to make something uniquely you!
Make sure the connectors on the mainboard near the damage area aren't damaged themselves first also. Decide based on all factors how much you want to spend if it comes to that.
Now last and honestly, I haven't worked for an OEM PC manufacturer in years. Their policies may have changed. The big question that I don't know about (and you may ask when you call in) is if by replacing your cosmetic components and power plug somehow changes the terms of your warranty for future problems. It shouldn't (right of self-repair, etc.) but if you damage something further, that of course would be on you.