I had all the parts necessary to carry out my engine buildup.. I accumulated them over the course of a year (I was in no rush) and by the time came to strip the engine down and build it up again with stronger parts, it only took 3 weeks from dropping the car off, to towing it to get tuned.
Where engine builds get lengthy, is when you are forced to sit and wait for parts that you ordered DURING the build and are at the mercy of the parts supplier. The actual labour itself can be completed in 2 weeks.
As for what's better, rebuild it or buy another second hand engine, your engine is probably the newest you'll find on the second hand market for a decent price. Most of them are from R32 GTRs or older R33 GTRs.
I would stick to yours, diagnose what went wrong, price out a rebuild and then make a decision from there. A replacement RB26 can cost you anywhere from $5000 - $8000, and upto 16,000 for a new one.