Don't be afraid to submit your query for review, even if you know it needs work. This is a great way to validate where it needs work the most.
I'm projecting my own experience onto you all when I say the biggest fear is that someone will find something that warrants a re-write in the manuscript, and none of us want to go through that (again!). But truth is, if it's needed, it's needed. And you're better off knowing where it's needed if you want to sell your manuscript.
That's what agents and editors look for. What will sell. Even if it's a sold to a smaller audience, like many argue the true "literary" market to be, if it is a known market and there is predictable revenue from the sale of your manuscript, agents and editors will put it on the market. You may get a smaller advance and less overall income, but you'll get the sale. If, of course, the manuscript is up to par.
I know that when I give advice and criticism, a lot of it is filled with nuggets I gleaned from the agent and editor blogs. Not plagiarism - just learning from them and re-telling their wisdom in my own words. I do it for people who may not have seen that particular post, or follow that agent's blog It's a great way to pass on valuable information. Plus I do have my own ideas to share...
The link to submit is at the top right of this blog.