Welcome to the forum!
There are kits out there that are supposed to be drop-in solutions for DIY LED setups. I have not used these, myself, but they do appear to have all the necessary components covered.
When you ask about DIY, it really depends on what you're comfortable doing and what tools you have available. Do you have a drill (preferably a drill press), a tap set, cutting oil, multimeter, and a pencil-style soldering iron? Without a soldering iron, you're going to have to look at a "solderless" kit or buy solderless connectors. Without a drill press, you won't be able to buy a blank heatsink and customize holes where you want them. While it's possible to use a hand drill, it's very tedious to do by hand. You'd have to use thermal epoxy to permanently glue LEDs to the heatsink. If any of that sounds bad, buy a drop-in kit.
There are many writeups with lots of info available online. Bill at ReefLEDLights.com is a forum sponsor who is active on R2R. His site has a nice info section as well. I'd also recommend RapidLED.com's "LED University" section, which has a guide for the BioCube 29 (both Oceanic and Coralife varieties).
