In general I'd say the C-41 kits are relatively simple for someone who's accustomed to B+W development. It comes down to being sure the chemicals are at the proper temperature and that agitation is even. There's much less tolerance for variation compared to B+W but it's still well within the reach of a diligent amateur who focuses on reproducibility and good lab skills.

The main requirement is a temperature-controlled hot-water bath for warming the chemicals, which are relatively easy to construct with some creative use of aquarium equipment. Buy yourself a digital thermometer from Amazon to verify your chemical temperatures (you should have one anyway for B+W development).

You may also want to consider a rotary development instead of hand agitation. If you can find a "roller base" unit, you can just place a standard developing tank on the rollers and it works fine. I love mine for B+W development too. Works like so.

https://www.youtube.com/watch?v=60rYmqkyfDg

E-6 is a little more complex than C-41 and I do not recommend the DIY kits in general. The DIY kits are a simplified 3-bath version of the full 6-bath process and has negative consequences for quality and long-term stability of the resulting slides. Since it's more difficult and the finished product is inferior I recommend just getting it commercially processed.

You can send it out at most supermarket photo centers, just mark "E-6 Process" on the "special instructions" box. It all gets sent to a processing company (often Fuji) and they know what to do with it. Nobody does in-house ("1-hour") processing anymore, sadly.