Your best bet would be to find a designer running Solidworks IMO. The software is cheaper to buy/own as compared to ProEngineer or Catia and it's still very capable. Whoever you hire on, just make sure you own the 3D model and drawings after the design is done. If you ONLY get a set of engineering drawings after the job is done and you need to make changes 2 years down the road, you might have to re-create the 3D model. Make sure you get a complete package back.
I don't know current rates for Solidworks, but Dice and Monster.com should give you a ballpark number. Each region has different rates.
__________________
Rick
-----------------------------
"Better to Be Lucky than Good "
|