The only limits on downloading is what your scanner is capable of holding. I don't believe the subscription service has a a limit on how many times you can do downloads. I've done a ton of downloading and haven't seen any problems.
There is a learning curve when it comes to digital trunked radio systems what is what you wish to monitor. They are much more complicated than the old conventional analog systems with many more settings to make.
In a simplified nutshell, you program the control channels in your scanner and they pretty much run in the background. You really are not "listening" to a control channel - it's the talkgroups on which your attention should be focused.
Unfortunately my Minnesota residency ended years ago and my specific knowledge of your area is limited, so some of my assumptions may need refinements from the local folks.
Presuming you are in the St. Cloud area, you'll want to program in the following frequencies as control channels:
859.0875 (the primary control channel)
856.9875 (an alternate control channel that may be used from time to time)
857.4375 (another alternate control channel)
857.9875 (another alternate control channel)
You'll then next program in the appropriate group area of your scanner, the talkgroup ID numbers for the folks you want to listen to. For example, the Saint Cloud police dispatch talkgroup ID is 24444.
What will be happening in the radio system is this. A St. Cloud police user keys up his radio. The controller sees this request to talk and "tells" all those having their radios on talkgroup 29444 to switch to an available voice channel (for example 852.30000). The radios automatically make this switch and the conversation proceeds.
Your scanner will pretty much do this same thing - it will be receiving the voice channel that has been assigned by the controller (via the control channel) to the selected talkgroup which we used 29444 as the example.
The bottom line is that you have to do some tinkering and through trial and error, you'll ultimately end up with having what you want. Using programming software and a subscription service will make things simpler.
The thing to bear in mind is that with the 396T is different than the other Uniden digital scanners. It is only capable of one system/site. If you have the ability to receive more than one system/site, these will have to be programmed as additional systems in your scanner. By that I mean if you are close enough to hear the Hennepin West system, you'll have to program that separately from the St. Cloud system.
I'm taking the phrase "I haven't scanned for a while" to mean that you might have been in the hobby years ago and are now picking it back up. A lot of things have changed. Scanners are more complicated and they have a learning curve. Plus the Minnesota Armer system is a complicated system with lots of ins and outs with it. So that adds more learning.
The bottom line is to have faith and patience - pretty much everyone gets the hang of both.