Hey David,
To accomplish what you are suggesting would require a bit of cutomization of several tables and screens. I can give you an idea of how to do this for Invoices, but this will work for Purchase Orders and Estimates as well.
Editing the Invoice Line Table
1) Go to Customize -> Tables / Fields -> Click on InvoiceLine.
2) Click Add a Linked Field and select the Invoice table
3) Select the fields you will want displayed and click Add Field.
4) Repeat steps 2-3 for each field you want to be displayed
4) Click Finished Editing Fields
Editing the Item Screens
When you click "Go To.." on the list screen, you could be redirected a number of different screens based on the item type (Inventory, Non-inventory, Service etc..). If you use a many different item types, you would have to add a "InvoiceLine" grid to each respective screen (ItemInventory, ItemService etc..) Alternatively, you could create the "InvoiceLine" grid to the Item List screen for all items. The process is very similar, but I will show you how to do it for the Item List screen.
1) Go to Customize -> Screens -> Click on copy for Item List.
2) At the end of the copy wizard you must select the Replace links to an existing screen option so that this screen will appear everywhere the orginal Item List was linked, essentially replacing it where it's used throughout the CRM.
3) The new Item List (2) screen should now appear in the Screens List. If you click Edit the Screen Designer will open. From here you must find the Item grid and click Edit.
4) Click Next to go to Step 2. Click the Link radio button and by default it will populate a "Select" field. Click Insert Column and then click Finish.
5) Next, drag a Grid object from the Add Objects tab and select Edit.
6) Name the grid, make sure Attached is selected and choose InvoiceLine from the dropdown. Click Next and select the Field radio button. Add your desired columns and click finish.
7) Publish the screen. Then browse to the newly created Item List screen. You should be able select an item, and the grid below will populate the related invoices.
To get the same results for estimates and purchase orders repeat the steps above, but replace the InvoiceLine with EstimateLine and PurchaseOrderLine. Hope that clears things up a bit.
Sam