Hi,
If you want both billing and shipping address ; you will require the shipping step in your checkout workflow.
You will also need to force the shipping regarless of the weight.
After that, you can just have one single shipping method with a free price ; so it won't influence the order total.
About the display, instead of CSS you can use view override.
And for the email, best will be to override them too ; so you will be able to remove the references for the shipping.
For the payment, if you want to have a quotation system, best will be to remove the payment step from the checkout workflow. Orders will be created at the end of the checkout and you will be notified by email.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.