The standard stock report will give you that info. Just go into reporting, Products, and run the first report, Stock Quantities: Standard.
For all products at a particular location select "Product" and specify the "Stock Location", i.e., 3. before pressing Next> and then Print or Preview.
For total value you can just skip to the total calculated value on the last page. Also make sure you select the correct Base Price, i.e., Average Cost or whatever is required.
For particular groups of products select "Stock Groups" instead of "Product", then tick the groups you want to report on.
If you want to report on all locations for all groups leave your Stock Location box blank.