does any one know roughly how much it would cost to replace an older furnace and central air unit. Buying a house with an older one and just wandered roughly what the cost would be.

Depends on capacity required, type of fuel, complexity of removal and installation of new unit, lots of factors. Does the condensing unit need replacing, too? Get a local estmate from someone who has seen the installation.

Everything Richard said, he always has thorough and thoughtful advice.

I'll be less thorough. $3000 absolute minimum for both, cheap, quick and dirty, $8000 for a top-line, high efficiency replacement set with bells and whistles.

Get a few bids,buy the best you can because as fuel costs rise,it does payback and pollute less.