network

i currently have two buildings, 250 metres apart, i am currently designing my network which will consist of 250 users in one building and 120 users in the other i have two windows 2000 domain contollers and one linux server, network traffic is expected to be high between the two buildings, i will also need connectivity via my isp, i now need some expert advice on how to connect all this together, could you please give some advise and guidance on how to accomplish this

thankyou
dave cuming