I don't know if what you are talking about doing is actually legal on ebay. Trying to decipher some of their regulations and guidelines is quite confusing sometimes..
I do know that you have to list a 'set' product for an 'auction' listing. For instant, 'men's green sport shirt, size large'..
You cannot list a 'men's shirt', and then say in the auction description to 'email for the size and color you want after the auction'. That is illegal and they will pull that auction...
Now with the knowledge that you do have, you could offer a ebook on how to make certain repairs for certain common problems on different types of appliances that you know about.
People often would like to be able to make simple repairs, but don't really know how to go about it or what types of indicators to look for and things like that, so they just call a repairman...
You however know about all of those things. That being the case, you could easily put together some ebooks, 5, 10, 20, however many that you think you would need to cover different types of common problems that they could fix using your guide..
You would only have to create these ebooks once, yet you would be able to sell them over and over again..'Create it once--Sell it forever'.
Just look at that guy on ebay who is selling the ebook on how to adjust your carborator to get better gas mileage. He has about 5 different ebooks covering different popular car models and sells a ton of them...Also the guy who is selling the guide to make you car run on propane by just changing a few parts,, he's doing extremely well..
I would check with 'ebay live', and find out if you can in fact do the type of listing that you are talking about before do your listing. If they say no, then you can still do some ebooks, or just do an ebay classified ad. It's legal to offer services in that format. Plus in the classified ad you can link to your site for direct sales if you have one..