.net - Memory Usage In WPF Application - How To Track And Manage

I have a small-scale WPF application using VB.net as the code behind and I want to add certain features, but i'm concerned about performance.

1) My app interacts with a third party database to display "realtime" data to the user. My proposed method is to create a background worker to query a database every 30 seconds and display the data. I query about 2,000 records all long integer type, store them in a dataset, and then use LINQ to create subsets of observable collections which the WPF controls are bound to.

Is this too intensive? how much memory am i using for 2,000 records of long int? Is the background worker querying every 30 seconds too taxing? will it crash eventually? Will it interfere with the users other daily work (excel, email, etc)?

2) If an application is constantly reading/writing from text files can that somehow be a detriment to the user if they are doing day to day work? I want the app to read/write text files, but I don't want it to somehow interfere with something else the person is doing since this app will be more of a "run in the background check it when I need to" app.

3) Is there a way to quantify how taxing a certain block of code, variable storage, or data storage will be to the end user? What is acceptable?

4) I have several list(of t) that I use as "global" lists where I can hit them from any window in my application to display data. Is there a way to quantify how much memory these lists take up? The lists range from lists of integers to lists of variables with dozens of properties. Can I somehow quantify how taxing this is on the app or the end user?