While you won't be able to replicate your system face exactly it might be possible to replicate it close enough that it will pass your own critical inspection. Just how close you'll be able to get depends on a number of factors, not least of which is what your system head actually looks like. If you have specific features that cannot be replicated by a mesh head, then you may get close but not quite close enough for your liking. Only you can decide whether that's worth the work, but it is worth a try.
To begin with, you need to ensure that you look for a head that's marketed as a 'Bento' head. Bento heads allow you to use your system shape sliders to manipulate settings on the head. Depending on which brands you try, you can use approximately 30 sliders (give or take a few) to change the shape. Some heads are more responsive to the sliders, too. A setting that's very sensitive on, say, a Catwa head might not be as sensitive on a Lelutka head.
Secondly, you need to begin with a head that has a similar base shape to your system head. For example: if you have a very pointed system jaw, you may struggle to get the same jawline from a mesh head that starts out with a strong square jaw.
Don't forget that - just as with system skins - the right skin applier (and any accompanying additional appliers, such as makeup, freckles, age lines, etc) can alter a mesh head, to the point where 'almost-but-not-quite' becomes 'well damn that's close enough for me!'
There are many brands of Bento mesh head out there, from the big names such as Catwa and Lelutka, to smaller ones that are quickly rising (such as Genus) to the much lesser-known (and catered-for) ones that will necessitate the use of Omega cross-brand appliers because people don't create appliers for that particular make of head.
For most Bento mesh heads you will need to start out with the included 'starter shape' which you then edit. This is because of the way that Bento heads are rigged. There are some heads (such as Utilizator's Normie head) that you can put on over your system shape, so that might be a good one to begin with.
When it comes to editing, a good tip is to get on a posestand and cam close to your avatar (don't scrollwheel; instead hold down CTRL and keep tapping the zero key until you're cammed close. CTRL and 9 will reset your view) and take a closeup face-on snapshot, followed by a closeup profile snapshot. Rez a prim and bring it up to the same level as your head. Texture the front of it with your face-on snapshot, and the side of it with your profile snapshot. You can use these as guides to help you while you play with the sliders.
The best advice is to demo demo demo. Try lots of head demos, together with lots of skin demos. @BelindaN's thread on this forum is a great example that shows how someone moves from a system head to a mesh head with the encouragement and help of others, learning about mesh along the way (and ending up as a very dedicated shopper!) -
Incidentally, I was the biggest b!tch going about mesh heads, way back. I can point you to blog posts that I made wherein I railed against the infernal things endlessly. I was never going to wear one all the time until I could find one I could make exactly like the system head that I'd spent 9 years wearing, everyone wearing them looked the same, etc etc. I was a crushing and bloody annoying bore about it.
Then Bento came along. I tried a few demos, but still none of them stuck with me. I could wear them for 5 minutes, but then Skell would be screaming "GET IT OFF ME!" But finally, in January of 2017, I found a head that I could wear for more than five minutes.
I didn't take it off - until I bought another, and then another - and I now work as a CSR for that first head's brand
Looking back now, I've come up with an analogy that works for me: I look at moving from a system head to a mesh head as akin to growing older in real life. My reflection in the bathroom mirror these days isn't the same as it was back when I was 20. I've matured, and - while my general features are still recogniseable - I don't look the same. In turn, Skell has just evolved and grown older in Second Life. I now use mesh heads of all brands and shapes as fashion accessories, and change my look all the time.
I hope you find the right 'you' in the world of mesh heads, but even if you don't then I hope you have fun trying. Don't worry about being excluded from places that don't want you because you're not 'meshed-up' enough. Find the people who want what's inside, not what's outside.