So you decided to go with the TDK veloCD?  Cool.  I'd like to know what your experience is with that burner.  The only special thing that I can think of for you to consider when installing the drive is to pay attention if your Creative 52X CD-ROM was master or slave and match the TDK burner with that.  Other than that, it's just like what you said...plug in the power, hook into the IDE cable, perhaps include the audio cable too.  Oh yeah, make sure that DMA is enabled in the properties window once you finally have the burner in place.  I'm curious, what other CD-ROM drive do you have that would make you want to replace the 52X CD-ROM with the burner?  I like the speed that the Creative drive reads at.  Do you have another CD-ROM hooked up too?

In regards to the Nero upgrade to 5.5...I upgraded to 5.5 and it went off without a hitch.  So you shouldn't expect any nasty things with that upgrade.

I have an HP P1100 that uses a USB cable too.  I tried both cables (gold plated and regular) and I didn't notice any difference as far as performance is concerned between the two.  I would suggest for you to just save your money and just get the regular one.  Well, hope I've helped out some.  Let me know how your upgrades go!