Experiment! Before you say how bad you are, how much have you really had a chance to do it? Very few people are good at something the first few times.
If you don't want to risk loosing some of those you could always pick up some hardboard or such to do mock-up work on until you are comfortable. And don't start with anything too complex obviously. And of course don't expect your early attempts to come out looking like some of the amazing things you see posted by the terrain veterans here. I'm sure you will find that after a couple tries you are making gaming terrain pieces that you can be proud of and happy to play with and they will be better each time. I just did my very first terrain piece myself and though it's not exactly what I was visioning I'm happy with it. My wife and kids are really impressed which helps soften things too. I hope to actually game with it in a couple weeks.
Regarding that awesome find...you're sure they're new? No fishey smell?
I wonder if it was a case of some production issue where they couldn't be used in the restaurant. Anyway, their loss is your gain. I've seen a big variety of those. What are yours like? Square vs. rounded. How large and how high the legs? Keep us posed on what you try!!