Buy some insurance, get an equitable written contract with the client, and do it.  It sounds like you have access to a team (engineers and contractors) that can get you where you need to go.

Take the bull by the horns!

Why do you want this project? Will it compromise your current employment? Do you have a mentor who can check your work? 

Go for it. It's residential, so significantly lower stakes than commercial, and a good way to learn. I will tell a story of my first-ever residential side job, take it as a warning:

Kitchen remodel. Client selected a slightly fancy backsplash tile. I figured out how much she would need to purchase to  help her figure out a budget estimate so she could decide whether it was worth the extra X dollars to go for the fancy rather than a cheaper option. She decided to go for it, and then when the contractor asked me how much of the tile he should order I stupidly told him how many SF I had used for the budget figure.

Six weeks later as he was installing he came up short of material. I had not calculated additional for cut tiles where the backsplash met the cabinet. Total rookie mistake. But what I learned was to never, ever tell a contractor how much of something to buy. Show them the drawings and let *them* figure it out - that's their job.

Be sure to verify that you current employer allows moonlighting. 

Keep in mind that unless you have insurance, a well written contract, and establish an LLC your client can sue not only the firm you currently work for but go after your personal assets if anything goes wrong.  

Any profession requires you to take leaps now and then.  

Hey cdimey. I'm out of college the same amount of time as you. I had the same opportunity a year ago and turned it down.

You should consider the positives of taking the job on. From my perspective I had a lot going on: I was studying painting part time and developing research proposals for grand funding. I concluded that focusing all of my energy on what I was doing would get me further with the kind of practice that I wanted to pursue in the end. Ask yourself whether taking this job on will get you to where you want to be. Don't look back in a year and regret not having taken the job. 

Also consider working on the project with a friend who is in similar circumstances. The support from someone in similar shoes is comforting. It will also ensure that you have someone with whom you can have meaningful design conversations. It's very easy to get caught up in the realities of building construction and to forget about your design ambitions. Having a partner will allow you to more easily make space for architecture, and to identify where you need to outsource for more expertise.

Prioritise short term discomfort for the development of your personal practice in the long run, you'll be better for it! 

Take the job.  You only get one chance to grab the brass ring.  It will be a huge learning experience and you will make mistakes, there is no such thing as a perfect set of drawings that is why you need insurance.  You have to have a tolerance for ambiguity to do this work, every project is different and rewarding in different ways, but you will never find out unless you allow yourself to push beyond your current limits and allow yourself to grow.  

Better to be the head of a chicken than the tail of a ox. 

This is such a classic debate.  I started when a potential client came to me and sold me on taking the job. He basically said "look someone is going to do the design, get paid for it and if it's not you it's somewhat may likely do a shittier job so I might as well pay you to do a good job."

The pay was fine, it wasn't a cheap job nor did I get rich but it gave me the best and worst experiences of my early career and set the tone for much more work.