config the login

hello there, nice 2 meet you all here in this community forum.

i?′ve got a little problem i can?′t handle myself….i need your skills.

i?′m using wordpress the first time and i?′m very happy that we both fit together. its very great and the best i know and…..THANX.

the problem is, i want tweak the login that it will fir to my template….the same background u can see on the mainsite, the same border colour and perhaps a smaller font.

how i can change the bordercolor and positions i found in the admin.css in the wp-admin folder.

but the background on the wp-login.php i cant change. the question to you is…..where i have to change this. and is it usefull to change it, i ask myself will this be a problem in future to update wordpress?

i?′m using wordpress 1.5 strayhorn with the default template.
thanx 4 your tips, hints and answers

cheers and gn8