I would start with fully bullet-proofing the good old 6.0L, and investing in a quality monitor (Edge Insight CS/CTS cant be beat)
Write Up: Bullet-Proofing the 6.0L PSD.
After that (determining weather to keep or delete the EGR cooler, and weather to put in that remote oil cooler from BPD) its gonna eat up most of that 8k you're figuring on having.
Long term plans, it depends on how much power you're looking at wanting to put down.
Here's a very basic layout of power bands and mods:
420RWHP - SCT tuner with custom files and a 4" turbo-back exhaust (literally its that easy)
475RWHP - Step up to 155cc Injectors, Powermax (stage I), and a regulated return (a aftermarket fuel system isn't required) If you tow heavy/often, this is as hot as you're going to want to run.
500+RWHP - Step up to 175cc Injectors, Powermax (Stage I), and aftermarket fuel pump with regulated return.
540RWHP - 190cc Injectors, Powermax (Stage I) and aftermarket fuel pump. This will tax your Powermax turbo and your transmission. A stage II turbo would be a better choice for this set up to get the most out of those injectors. For the transmission, you'll be wanting to get the funding put aside to build it up and install a new TC.
There are so many variables in performance past this point that its hard to lay anything concrete out here. I hope this helps, and look forward to reading about your updates.