you could prob do it yourself i did a puma front wheel bearing and it was relativly easy you would need a bearing insert tool
http://cgi.ebay.co.uk/WHEEL-BEARING-...item2eac239205
just clean all mating surfaces with emery papaer then oil them up and gently and evenly inserrt the bearing with the above tool
or take the hub of the bar and take it to garage it should keep the cost down