The biggest difference you will find between 44mag and 7mm mag is in the sizing and trimming required. With the 44, basically you run the case through your carbide sizing die and you're done, ready to prime and powder. With the 7 mm, it's way different.
To begin with, you definitely have to lube your cases before you run them through the sizing die. Otherwise you will DEFINTELY stick the case in the die. I've tried a few different lubes. RCBS lube2 worked well but it's a messy process. One Shot worked out OK for me, but I could feel a few times where I was almost about to stick the case. I have settled on Imperial sizing wax. Easy to do and no mess.
So now you have a case sized. Unfortunately you have to remove the lube you just applied or it will gum up the works. You can tumble again, or in my case I wipe it off with an alcohol-soaked rag. Not too bad.
For a long time I full-length sized my rifle brass. But I finally tried neck sizing for my .243 and .308 and I really like it. No more lube! I am thinking of giving that a try on my various magnum cases too. But to begin with, the safest thing to start out doing is full-length sizing. Eventually, you will have to do it anyway, so start with the basic way and avoid the shortcuts.
So now you have a perfectly sized case, it is absolutely critical to trim them down to the correct length. You see, every time you are bumping that shoulder back to spec, the brass has to go somewhere and it goes into the neck, making them too long. Trimming is a real pain. There are a myriad of ways to trim, each with their own benefits. Personally, I went with the Wilson trimmer with the drill adapter and it works good. But now I've discovered the Possum Hollow with the drill adapter and it's a lot easier.
This is where you'll discover why you really need a set of calipers. You didn't need them with the .44 but you will now. It is absolutely essential to get that trim length right.
But you still have another step to do. You will want to chamfer the inside and outside of the mouths of the cases to remove those burrs caused by the trimming.
Finally, you can prime the cases and put powder into them. As a general rule you will find that rifle powders come out of the dispenser a lot more inconsistently than pistol powders do. So you will spend a lot of time trickling powder into your scale pan to get the right weight.
Now when you get ready to seat the bullet, the actual seating operation is the same as a pistol, but the seating depth is a black art. You dont just seat to the cannelure and be done with it like your .44. They publish a standard overall length for your cartridge and bullet, but that's just kind of a rule of thumb. Your accuracy will be influenced by that depth and you will have to experiment in increments to find out what works best for your rifle with that bullet. Again, here is where your calipers come into play. You might as well start with the "standard" spec length, but you have to measure closely to make sure you have that seating die adjusted right.
One step you DON"T have to do compared to your .44 is to crimp. No need, in fact it can have a negative impact on accuracy.
As for bullets, I have found that different bullets of the same weight have drastically different accuracy. For my 7 mm, I found the best luck with 160 gr Sierra BTSP and 150 gr Nosler Ballistic tips, but that's just me.
For powders, it will be in the slow burning end of the spectrum. For me, I have had the best luck with RL-22 and W-780. But I had pretty good luck with H-1000 and Ramshot Magnum as well. H4831 is another good one as well as IMR-7828. A lot of choices out there, but for me, the particular powder was secondary to the bullet I used. Naturally, the amount of powder you use is extrememly important to the accuracy you get.
