VERY

At 600 miles everything has shaken down / settled into place and you need to verify things are correct before you put on a few thousand miles and destroy something.

Get a set of feeler gauges. Make sure the .003, .004 & .005 inch are included. I remove them from the set & bend a 90 about an inch from the end & roll the end into a bit of a "ski tip" shape, to make it easier to slip between the valve adjuster & valve. Also, a 90 degree screwdriver will reall help, as that will allow you to control the valve adjuster at the same time you are tightening it, keeping the adjustment from changing when the nut tightens against it. The slack in the threads WILL affect the adjustment some. I use the .003 on the intake & the .004 on the exhaust, since they get hotter, I give them a but more freedom.
I have almost 15,000 on my 05 S40 & have not messed with the head bols retorque. Just did the cam chain & had the top off & Couylda done it, but didnt,, not gonna worry about it. You may want to, tho I think most have stated there was no change when they went in & did that. No change I mean everything was torqued. You make the call.
Have fun! It's a breeze to mess with this bike till ya want to pull the carb, simple as it is, it's a pain,,

I would round up all the stuff & get on it. If the valves were way loose you would surely be hearing them. I expect all is well, but it is time to look. Have you changed the oil? i CANT REMEMBER WHEN A NEW ENGINE IS SPOSED TOI GET THE FIRST CHANGE. WAS IT 500 MILES? OOps, danged cap lock, not strtin over, sry.

yea i changed oil at 550 miles and yes that set would make it easy. no i dont hear the valves but do hear speedo buzz.

well i have a 150 laying around but that would not help you. yea i am going to do the valves hopeful on tuesday that is my next dayoff. and all my tools are at work.