Don't know any guide, sorry. I'm just a dev who had to figure out all of that because of the same reasons.
There's no file removing needed. What I would do is once you get a copy installed (such as 1.6) do a string search for curl and/or file_get_contents. That'll quickly bring up any outside calls which you can then investigate. The advertising ones are protected so you just have to edit the core file it's in and do a return.
Also, there's a fork of 1.6 called thirtybees : https://thirtybees.com/
Highly recommend you go with that over Prestashop. Not only are there performance problems with actual Prestashop, there's also security issues which are fixed in 30bees.
I'm self taught and unfortunately don't have any JavaScript experience. I have implemented Shopify into my stand alone website through their API. I have used other programs like prestashop.
I just found out about this thirtybees
Have you looked into that at all?
Just to add: thirtybees can be migrated to from 1.7 now, thanks to them joining up with Cart2Cart (not an advertisement, it's just a good service) - https://thirtybees.com/migrate/prestashop-1-7-thirty-bees/
You can actually select any number of different CMS and choose the things you want transferred to your CMS of choice and they'll do it for you.
Side note: Personally I'm using WooCommerce for a few projects as well, and it's just as scalable for large numbers of products. Personal preference at the end of the day. thirtybees would definitely be my goto choice if the option was PrestaShop or thirtybees though.
Frustrated with Prestashop and unhappy with the direction they are going with 1.7? Come check out Thirty Bees, a fork of Prestashop 1.6. Development is moving at a very rapid pace and IMO in the right directions.