"unpasted, washable, strippable vinyl wall paper" means that it is vinyl wallpaper without paste applied on the back by the manufacturer. So you will need to apply the paste yourself, instead of the somewhat easier application process of submerging in water to activate the pre-applied paste.

Here’s a close up.

This looks like the same wallpaper

Compare the bids, that is how you will know what is reasonable in your area. Know your budget, if they are too high have a back-up plan. That Nursery is beautiful, but to be honest babies don't really care as long as they have food and love. It probably looks just fine without any remodeling needed. I can't tell you what is reasonable in the North east if I live in the Upper Midwest. Materials vary widely because of the cost to get them across the country, heck even getting them off a boat right now seems hard. Make sure whomever you chose actually can get the materials and the subs to do the work if you are needing it done before the baby arrives. People are booked out, and materials can be delayed by weeks or months. Put something in the contract to cover you if its not done on time, maybe even have a lawyer read it over before you sign anything.