Don't fret to much over the cost to revamp your road bike, mate.
With gas cost what they are now the payback time will "pay"
for all the parts /labor fairly quickly. Besides, you really like
the bike and folk's waste more money than what you spend on
stuff that won't be around later as your bike will.

Money spent on bikes that are ridden reguarlly is never a cost.
It is a resonable investment in your health and well being while
costing nothing more to use (except normal wear & tear). I
can think of LOTS of ways to waste that amount of money.......
Can't you????