Customizing pedit?

On the profile editor page, we are collecting payment information for our members, and I had a couple of questions on how to customize the page beyond just adding new fields:

1. Some information is sensitive (CC numbers, Tax ID numbers)... how can those be made ****'d out except for the last 4 digits? A "password" type input element puts **** for the entire box, IIRC... we want to display SOME information so that they can see at a glance if it's OK, but without having all that information out in the open on the screen. I'm thinking the way to do it would be capture the info in the database before it is rendered to the screen and store the ACTUAL value in an input hidden field, and then do a strig sub for all but the last four characters to replace letters/numbers with the * character, for display in the input text box itself... then when the form is submitted, check to see if there are asterisks in the text box and if so, just use the "clear" information in the hidden field, but if not, use whatever was keyed into the text box (this is assuming they made a change). I am not sure how to go about catching these customized things before the page is rendered. Easy to capture it after it's sent, where the query to the database is written, though.

2. We are giving folks the option of paying by e-check or credit card. How can I either present one or the other (depending on which radio button is selected) and THEN indicate those fields are mandatory, while not making the others mandatory? As it stands right now, NONE of the fields are mandatory, based on the field customizing available through Dolphin's admin tool, because I don't know how to make it one or the other. I guess I could motify whatever JS is validating the form and add something that switches "required" icons from one to the other when they click the radio options between echeck or credit card. What am I missing here?

Basically, I want more control over the pedit.php file... maybe it's time to develop a standalone version of it that's not so totally hooked into the rest of Dolphin. Is that advisable?

Thanks :)