Change Width of Joomla Template

Joomla 1.5.x with custom template installed and working. The website has about 20 pages. The existing Joomla template has a width of 770 px. Width of template should be changed to 1024 px. CSS should be adapted accordingly. Index-page should be adapted if necessary. Adaption of subpages if necessary would be done done in a second phase (not this project). Only for Joomla experts. I can show you url in pmb.