I know you asked about the form (its what everyone thinks is the most important), but I always look at the tables and when there are issues there I go no further. You have issues with your tables.
The big issue is that you are not letting the database work for you when it comes to keeping track of inventory. [QuantityInStock]/[StockLevel] shouldn't be a fields in tables. Values you can calculate should be calculated and not stored--those fields and the action queries you have supporting them shoudl go. When you need inventory levels you simply add up all your credits and debits to your inventory in a SELECT query.
Also, you have too many tables with data about parts and you are not storing the right information in them.
tblParts - By its name this table should just list data about parts (name, description, type), but you've crammed in data about Vendor, order and customer. This table is doing more than its name and would be better named tblTransactions
tblInfo - this seems like what tblParts should be--just a listing data related to parts
tblinventory - this table should go away and instead be replaced with a query based on tblTransactions. [Minimum Stock Level] should go into your parts table.
You have additional issues that I need more information about to help you with. Location and Vendor data might require additional tables to accomodate. Can multiple parts be in multiple locations? Can multiple vendors provide multiple parts?
You need to address your table issues before proceeding with forms.