two prong outlets

Not expensive at all.

No, it's it's not a bad idea *not* to change them -- but it's often a nuisance when you try to plug in something with three prongs. Your local hardware store sells adapters -- but don't take any shortcuts, and be sure to ground them properly.

If the building was built in the 1960s, it should be wired with grounded armored cable and metal boxes, which in effect means that the wall box holding the outlet is grounded. So, swapping out the outlets should be inexpensive, and worth it.

thank you for your speedy replies. the building was built in 1960 so I'm hopeful I wouldn't have to upgrade the wiring.

Thank you for the fast replies. Built in 1960 so hope it's as nyc_sport says.