Here is a quick briefing on your website. If you agree with it, take the price I mention below as a good estimate. If you feel you need less, take a bit off the price... And if you need more features then you'll add, of course.

The website shall communicate your brand visually, and therefore the designer / developer shall spend time with you to understand your brand and the desired expression. you will also have to spend time to understand the desired "flow" on the website... Every visit should absolutely lead the visitor to an invitation to purchase or to book the repair service.

When this is done, the framework of the website can be designed and build in Wordpress or in something else. The developer / designer should add connections to your social media channels, opportunities for your visitors to engage et cetera.

The shop shall be built including an easy way for you to add products, update prices and shipping options, perform simple maintenance of your shop and monitor the shop's performance. The developer shall also integrate PDF invoicing, printing of shipping labels, and possibly a connection to your accounting system. I would assume you will be uploading the products, their images, and their data yourself.

The website seems to be largely finished now and can be tested, which takes time as you will have comments that will have to be implemented. The website also needs to be optimized: for speed and for security. The developer will have to be an expert in both fields, so your website will not be attacked and will be fast to load for everyone who visits.

Since you will want to be found in Google and the other search engines as well, your developer shall be an expert in "SEO" - Search Engine Optimization. And you will also want to get the daily and weekly analytics of the web site visits.

If hosting should be part of the offer to you, you will be looking for a certain bandwidth, server performance, memory and number of processors, with how many websites you share the server. If you want to do maintenance afterwards yourself, perhaps FTP/SFTP access to the hosting server.

Finally, do not forget some training on how to use the CMS (Content Management System), and perhaps an additional offer to perform maintenance and updates once the website has been launched.

Your briefing could include more, but based on the above I will develop the strategy with you, the design and the "construction" of the website and the shop, the hardening and security of it, and the hosting on our server. We will also help you to find a great domain name and register it on your name.
This way, it is a pleasant and inspiring process for you, with great involvement but no worries about the realization.

All included this will cost $ 6,000 plus a small monthly maintenance fee after the first year if you decide not to move your website away from our server. There is no need to pay anything in advance; as the work progresses you will look at our dev version and once finished we hand over to you and you make the payment.

As said, it could be more or less, depending on what your requirements are. But hopefully this helps you to think about how to brief a developer, and if you want to find out more, just let me know!