I am working on a website to sell furniture. We have set up our delivery options under Shipping Options but additionally want to add an option for the customer to purchase assembly as service. Customers should only be able to pick assembly once per order, ideally within the cart or checkout process.
We are currently using a custom form in checkout for customers to indicate whether or not they want assembly. However, this does not allow us to add the assembly fee to the total checkout price.
From what I've read so far, it does not seem to be possible to make changes to the checkout page, like adding this second fee. One option I am considering is creating a new service "Assembly" and then using a Product Block on the Cart Page. Is that possible? Any other suggestions for how to solve this?