Hi Phantom,
From your posting I can't tell if you've never grown any type of those fruits and vegetables or just that it is your first time with heirloom varieties.
I can tell you that if you've grown tomatoes before, and I'm assuming the same holds true for melons(I've never grown them. I'm allergic), there is no difference in what you should be doing whether hybrid or heirloom. Well, I should say unless you have a specific disease problem that cetain hybrids are resistant to, because then you may have to take stronger preventative measures. Black from Tula is a pretty popular variety. I have seeds but haven't grown it yet so I can't comment on taste.
If you've never grown any variety of them at all, I suggest searching and posting on the Vegetable forum for the melons and on the Tomato forum for the tomato. Many more people post in those forums and you will find/get lots of info. It will help a lot too if people know what zone/area you live in to give tips better suited to your growing conditions.
Remy