I think you're young enough to start over if you want to. If it's your dream, why not give it a shot?

If you're worried about your single engine proficiency, spend a few bucks (2 hours) on going up and doing some maneuvers or maybe going somewhere fun. Taking an instructor with you is not a bad idea. When I applied, I was more than current flying single engine 182's all summer long; however, I was woefully behind on my instrument and multi currency. What I did to prepare was brush up on all of my systems knowledge of the twin I used to fly. Then I started practicing on MS Flight Simulator to brush up my instrument skills. Once I was comfortable, I spent $200 on an instrument PC at a local airport. There are no specific rules as to how many approaches you have to shoot for an IFR PC...I think I did 4. My CFI/CFII status was still current and I didn't have to do 1-hour of IFR ground along with that, but you should prep yourself on IFR knowledge anyways since your airline interview consists of testing that revolves around your knowledge of Part 91 IFR regulations anyways. Check the gouges.

In short, get IFR current and do whatever flying/studying you think is necessary until you feel comfortable/relaxed. If you put the right amount of preparation in you will find yourself on the right track to success.

Is it worth it? Depends on your point of view, I guess. There is quite a bit of sacrifice involved....for me, all related to not being home as often as I'd like. But, I can't think of another time that I've ever looked forward to going to work in my life. I wouldn't trade any of it to go back to my "office gig"...sitting in meetings being force-fed buzzwords like "innovation" and "value"...and never create anything (just like those IBM commercials). Now, they can never take away my window seat.