I recommend picking up the Fuji CR6 or Kodak E-6 that comes in 40 to 100+ litre kits for not much more than the tetenal 5L stuff.
Helpful tips with the chems is divide down the mixing instructions to only what you need at the time: 300ml, 500ml, or 1l etc.
Not sure where you live.. but I find ebay to be the best source of fresh film, it has the cheapest shipping (only a couple of bucks for international shipping compared to $50+ US shipping ripoff from other places) and great prices, Provia 400X is about $3.60/AUD per 120 roll at the moment including delivery, Velvia 100 and 100f is about $5/roll I think.
First issue I can think of is the Paterson tank. I have the Paterson tank, can't recall the exact model, but it takes one liter of fluid. I can do two rolls of 120 in it. I would prefer the inversion method of agitation, but the Paterson cap does not quickly seal. You can get it on there, but it takes me 30 seconds to get it right without leaks, and that's too long to wait before agitation. So I use the stir-stick method with the stick provided with the tank. It seems to work just fine this way as long as you are firm - but not fast - with spinning the reels.
On the changing bag, I actually do better using one than without. Unlike in a darkroom, I can still see where my arms are in relation to each other, which is great if I'm snipping the leader off a roll of 35mm. I use the Arista bag from Freestyle. No issues. But give the darkroom a shot before you spend more money.
Finally, on temperature control, I use the Kodak E6 six-step process. Freestyle also sells this for about $55, but I'm unsure if they ship it. It really is a wonderful batch of chemicals, and is not much more effort than the three-step process. Also, I don't think you need any sort of heater if you have a sink basin that can (1) hold all of the bottles, and (2) has access to hot water. I do mine in the left basin of the kitchen sink. I mix the chemicals at the upper range of Kodak's recommended mixing temperature, then I stop up the sink and put them all in a hot water bath. I will have to drain and refill with hot water two or three times over the course of 30 minutes, but by the third time the sink temp is stable enough to do the whole process.
Before anything else, waste a roll of film and practice loading it on the reel !! -- no matter if you use a bag or do it in the dark you are going to be doing it by feel. Loading a reel properly is by far the most important part of the process. I can guarantee frustration and choice words at some point.
Just grab you reel and dummy film and watch some TV and load and unload that reel a hundred times before going into the dark with a roll of film you don't want to screw up. Watch for kinks, get a feel of how tight and how long the film is, get a feel for it loading correctly, get a look at not making half moon creases in the film as it loads...etc, etc.
* Just because your eyes are closed, doesn't mean the lights in the darkroom are off. *
* When the film you put in the camera is worth more than the camera you put the film in... *
* When I started using 8x10, it amazed me how many shots were close to the car. *
Thank you all for your suggestions! I am sure I will be back with more questions when the equipment arrives and I start. Thanks again.