DIY: Just make sure you do your research. Practice your soldering, make sure you know exactly what you're doing, be way too prepared for anything that could happen during the mod.

Buying pre-modded: Buy one from one of the big modders. Justin Thursday, Timbob, Boddah, People that have been in the business for years and have done that specific mod more times than they can count. A lot of the newer modders are just trying to get through the mod, where the experienced ones are most concerned about doing it well, and doing all the small things that make a difference in the long run.

On a side note, I, being jobless and poor, modded my own gameboys to save money, and it has worked out well so far. Also, if something goes wrong, I know how to fix it.

Good luck.

This is assuring, im working on one right now.

As long as you have at least a small amount of skill soldering (and almost no skill is required), doing your own mods is RIDICULOUSLY easy, and fun. I have done 2 DMGs, and neither of them have ever broken. Granted, I've never performed with either of them, but I have dropped both of them more times that I am proud of, or am willing to count. I was really nervous the first time I installed a backlight, but following Kitsch's tutorial, it went in very nicely. The biggest piece of advice I have is to go slowly. The first screen I did, I spent 45 minutes just to peel the foil off, to ensure that nothing would go wrong.

Also, doing your own mods is hella cheaper, which just adds to the list.

I agree

Modding is really fun. For me, it's part of the enjoyment of making music on Game Boys. But it's not for everybody. If it's more of a means to an end for you, I suggest spending the extra money and buying one from someone who knows what they're doing. You're supporting their hobby, and they're supporting yours. It's win win!

Agree 100%

Pay for projobs, diy for shitty shit.

I paid a decent amount of money to Timbob for a glowing painted DMG and I cant ever regret it. I did a shelljob to one used dmg myself and I cant ever regrt it.

I'd go with mod it yourself, not only do you get the satisfaction of knowing that you've done it, you also get the guarantee that if you cock it up, then you'll know how to fix it.

i'll help you!

Same thing happened to me.

Do it yourself, you'll save a ton of money $100 vs $30. Plus once you finish you will feel so accomplished.

If you know not what you are doing, better leave it for someone who does. I tried to go onto it on my own and found out it's not as easy as it seems. You may not have problems with things like pro-sound and similar mods, but peeling the polarized film when backlightning is a step further... At least for me. Soldering is easy, if you've had previous experience.
If you have money and don't feel like it, I'd say leave it for someone else. You'll get a very nice product and you're making someone else wealthier xD

I encourage you to build one yourself.
If you use best practices, your first successful mod will make you feel like you're f**king magic!
My worst problems came from a premodded DMG that I purchased... it was a mess in there.

the only one ive done on my own is an underclocking, and i hear thats the easiest mod to perform. i see no shame in getting someone else to do the hard stuff, especially if your worried about quality. unless money is an issue perhaps you could get a cheap little backlit and sounded gb then start investing in the stuff to start experimenting. im sure almost no one here could tell you their first mods were masterpieces.

Every DMG I modded ended up failing after a few months. 

Paid for some pro jobs.  Haven't had any problems.