Lid not closing & laptop not sitting flat

Hey guys, My 2018 mbp with Touch Bar isn’t sitting

flat on a table. This started 3-4 months back. I used to a put a piece

of paper underneath to stop it from being wobbly. Over time I’ve had to

increase the layers of paper to still make it sit flat! It seems the

laptop is getting bent more and more over time. The foot kit are intact

maybe the middle of the laptop has swollen.

I have also realised that the lid isn’t closing fully and about 2-3

mm open always instead of fully sitting flat. Took it to the apple

service center in our area they have told me the following:

The battery might be swollen. But the battery, trackpad, keyboard and

Touch Bar are all integrated into a single unit and all of them need to

be exchanged.

they would charge me Usd 450 for this repair. The old parts would be

kept by them as they’re saying it’s going to be exchanged and I am not

getting any new parts.

I have two main concerns:

1) is it possible only to replace the battery instead of all those parts?

2) do the apple service people keep old parts and what they are saying is it correct?

and can I keep the Mac running until I can or should I get it fixed

ASAP? This is my main work laptop and parting it for a few days as well

is really difficult!

Thank you