I know it has been a little while since you posted but if you still need help with updating your checkout you will find information on this here https://developer.paypal.com/docs/classic/admin/checkout-settings/?mark=company or https://www.paypal.com/cgi-bin/webscr?cmd=_profile-page-styles&CALL_FORM_UPDATE=false. This link brings you to PayPal’s developer page which contains lots of information on integrating PayPal with your website and updating your details.
Also below configuration may be done if you are using a Premier or Business PayPal account.
01. Log in to your PayPal account.
02. From My Account, click on Profile.
03. From the Selling Preferences section, open Custom Payment Pages.
04. Click “Add” to create a new Payment Page style.
05. Name your new template (use only letters and number, no spaces).
06. Upload your header or logo image to the images folder. If using a header, ensure your image has a width of 750px and height of not more than 90px.
07. Add the image settings within Paypal:
a) If using a header image, enter the secure URL for that image (https:// …) in the “Header Image URL” text box. If your banner has a white background, leave the Header Background Image, Header Border Colour and Background Colour fields empty. Click “Save”.
b) If using a logo only, enter the secure URL for that image (https:// …) in the “Logo Image URL” text box. Enter your desired color settings in the other fields and then click “Save”.
08. On the Page Styles screen, select your new style and click “Make Primary”.
09. Try making a test transaction on your website (you don’t actually need to pay for anything!). Once you reach your PayPal page, note your new banner or logo along the top of your page.