I have a form where I want to fill out a requester field which is a custom attribute that field will be the SamAccountName of a user would like a way to do a user picker or something. maybe like a java lookup tool.
The easiest way forward here is to make your custom attribute a DN syntax. When you add this attribute to a form, an object picker will automatically be available for selecting its contents.
On the backend, if you need samaccountname, you could setup a second (non displayed) custom attribute to hold the samaccountname version of the user's name. A small snippet of Powershell code could be implemented to perform the translation.