maintaining a freshwater tank is nothing too difficult, you just can't be afraid to put some time into it. Just like anything else in life, the more you put into it, the more you get out of it.
I would say that $400 is a good deal for all of that, is it a nice stand? because new stands alone can cost $400 for a 90 gallon tank.
For your filter you can choose to go one of two routes, either a canister filter or a power filter. Canister filters are much more expensive, but do a better job than power filters. My preference is an Aquaclear powerfilter though. I like this filter because it is set up like a canister filter but it hangs on the back of your aquarium. This filter also allows for a great exchange of gasses and airates the water really well, which is something that i don't think canister filters do a very good job at.
To maintain this tank, you can do water changes every other week, about 15 gallons. Or even better would be to do that every week if you want a thriving tank :)
If you keep things rather simple, then this will be a great project/hobby for a begginer!