** Is there anyway to route water and/or gas from the kitchen (or elsewhere)to install a washer dryer? **
Pretty difficult for anyone here to be able to tell you without seeing the floor plan. Try contacting a local plumber to actually check the layout you have. You might also need an electrician so if you can find one that does both, all the better.
** I know some people put their washer and dryer in closets -- are there usually existing hook-ups? **
Yes, but it may be possible to install some (depending on the home's structure). Wherever you install a washer, make sure there is *very* stable flooring or damage to internal components of the washer may result.
You can read some other appliance installation tips at the following link: