Unless you have an understanding of the testing regime, and have gone through the relevant standards associated with wireless and metering requirements (of which there are many, and all will appear quite intractable), and are sure that you have designed a product that would get through the worst of the hurdles, then you need to get someone familiar with product testing on board.
Product testing for approvals is not cheap, particularly if you have to go through a number of redesigns. A PE can't approve a product, only give advice. Even a PE could get some things wrong, I have been involved in product testing in the past, and there are lot of things that can and do go wrong. So yes, you should have a PE look over the product, but it needs to be someone familiar with getting a product through approvals.
By metering, do you mean power metering, if so there are additional hurdles to go through aside from the safety aspects, since meters have to meet performance requirements as well.
Wireless adds another level of complexity, you need to use pre approved wireless modules if you can, or be faced with another expensive series of tests.
Talk to the approvals labs, they should be able to give advice (for free, one would hope),
cheers,
Richard
