As I recollect $1K for the property survey required for my build. The price was high because all the lot demarcation pins from prior surveys could not be found. If you can find the surveyor who did the last survey you get the best shot at being able to avoid some extra cost. A quick discussion with the surveyor who did the existing survey on the property is a great place to start. If the surveyor is familiar with local zoning, they should be able to give you a good indication of exactly what variance(s) will be required.
Wetland exchanges in my area are allowed, but the exchange rate is 1:2 (for every sq. ft. of wetland you remove, you need to replace it with double the area).
Engineered plans are required for any structure above a certain size in my area. All the reputable builders are used to producing these and it is no big deal. If you're planning on doing the building yourself, unless you're handy with a decent building design program, you're probably going to need to have an architect draw up the plans. If you use an architect, you need to make absolutely sure you know what your final plan is going to be, because changes are going to cost you money. With a variance required it is possible that the planning board may request changes to anything you present. If your local planning board is flakey it is possible that several rounds of changes may be requested before you get approval on a final plan.
Generally using local surveyors, builders and architects for whatever you want to do helps make things go well. Outfits with good established relationships with the town and planning board know how to get things done and have already established trust. A call to your town to ask them who they use for their projects is an easy way to find out who has these relationships.
Given your location, the time of the year and the requirement for a variance, I'd say you're being optimistic to think you're going to get a building up this year.
