I think the duck logo is great,.. its easily noticed and won't be forgotten in a hurry,.. what more do you want?
As for the landline number,.. you could always peel it off again if you decide it isn't working out,... or leave it off for now and have the option of adding it at a later date. Its only sticky vinyl,.. its easy to change!
Getting the van signage done will make you look more professional and will definitely bring in more work. It'll pay for itself very quickly,.. and keep on paying for years to come.
If you are looking for more work quickly, you need to "brand" yourself, and make your brand known. I'd suggest a small flyer drop (5000 odd, and single colour cheap printing is fine for this type of flyer) with the same logo on the flyer in the areas your van is most commonly seen in,.. and maybe a couple of cheap ads in the parish rag. Even getting the logo on your work shirts might be a good idea.
I'm still getting calls from a flyer drop I did 10 months ago,.. so it's definitely worth it.