You local shop may charge different.. but I paid about $130 to get my 58 235 bored from STD to .020. On the high side I would GUESS that you'd have to pay for a bore, the liners/install, and a final bore... $350-400-ish?

I just finished my 235 rebuild and am at just over $1500. $600 machine shop, $800 master rebuild kit, $100 odds and ends (fuel pump rebuild kit, carb rebuild kit, new valve cover). Putting a motor together is not hard work... the biggest stumbling bock are the valve guides and harmonic balancer. Everything else is really just measure and assemble.