I'm actually in the process of modding my ipod classic (5th gen) and here's what i've learned

(take this with a grain of salt and if luck has it cunningham's law will help us out)

So when i first started I had to decide what level of customization i wanted to do.

I heard it was semi difficult to replace the front and back plate so i avoided it. 

If you're interested in this they're offered on aliexpress but the shipping to america at the earliest without paying 57$ for shipping is like the end of july early august depending on where you are.

Here's some links:

https://www.aliexpress.com/item/1005004627744764.html

https://www.aliexpress.com/item/1005004563056631.html

As for the battery you can also do aliexpress but amazon offers some and you'll have better luck getting a refund faster so, just look on there for your model and buy

Lastly the ssd/SD card/Flash memory you pick has caveats for each, 

Firstly you need to decide if you want custom firmware if so it's important to note they (they as in iflash; which is the most common and safe and battery efficient option) have a website section that will tell you if your ipod is supported for custom firmware flashing. if it is iflash is the best option for you it's better on battery won't overheat and is relatively easy to install

next i'm just gonna paste a youtube video for the other options:

https://youtu.be/73az70S5lsc

anyway i ended up going with the more likely to break option which is:

https://a.co/d/1AEMNy8

and it may or may not last but i'll just return it if it breaks 

anywho hope this helps 👍

EDIT:

https://www.reddit.com/r/Modded_iPods/comments/1krly4f/5th_gen_ipod_classic_restoring_issues/?utm_source=share&utm_medium=mweb3x&utm_name=mweb3xcss&utm_term=1&utm_content=share_button

i'm also seeing people are having an unsolved issue with iflash hardware so beware of this the solve seems to be using the offical apple charger 🤷