Setting Up an Online Retail Presence

To anyone willing to help, I am the fourth generation to come into the family business. This business is a local supply store serving the plumbing, oil, gas, coal, industrial, agriculture, etc. industries. I feel as if we have waited far too long to obtain an online retail presence. This way we can sell our products online to anyone in need, whether it be locally or anywhere in the continental United States. I have personally taken on the responsibility to build a successful website that we can sell our products, but I have no idea where to start.... I know there are services like Shopify, Wix, Etc. But I'm not sure If they would be useful due to the large and diverse inventory (around 5,000 different products) that we sell. Obviously I do no think that we would have nearly half of that on the webstore, but I am skeptical to how the services listed could handle that efficiently in terms of sales and what products to promote. Once again I have no background in webdesign, wordpress, or anything of the sorts. My initial questions are as follows;

• Would it be best to hire out the work of designing the store? or should/could I teach myself how to do this and save tons on paying someone?

• What are some general costs to hire someone to do this?

• As stated above, could a Shopify, Wix, Etc., handle this for us?

• Where in the world would I even start?

Thank you to anyone willing to pass along some information. Even an article to read would be greatly appreciated!