Ask HN: Need some suggestions on e-commerce for a racing engine shop

I've been hired at a racing engine shop to basically revamp their entire web presence. I've been working there for a while now but I'm having 2nd thoughts about what I decided to go with to host their shop. I went with shopify to replace what their previous computer dude had on iPage which is a horrible webhost. Before shopify I attempted to just use a WordPress but since I'm literally the only technically minded person at the shop and this is my first job, I felt it was a bit over my head to jump in to being responsible for SSL and payments. Well in between them having me work on irrelevant things like slideshows I've been educating myself in analytics. We don't get much traffic and I'm not a marketer or a sales person. Anywho, I'm going to be rambling in this post, apologies. Another thing is that they use a program called Sellwise as their in store POS which is offline and running XP and Sellwise is a DOS program. I have gotten that running in DosBox just in case I need to take it to my workstation and look up something. Anyway, shopify... Might not be the right thing for this. I'm just manually listing the stuff they had on eBay. They don't have a straight plan for what they want from me. So I'm pretty much free to figure all of this out for them. Most of their current customers actually are less single products and more I guess bill of materials type stuff. Engine builds. Services. That kinda stuff. Not repair mind you.

Oh what a good first post huh. I've been reading stuff on here for a while but never had an account, love this place, great New ideas always.

Edit: link to the website https://marolloraceengines.com