I think it depends on your skill level and comfort - me I am all about that sweat equity and why pay someone to do something I can do myself - with one caveat - if you can do it room by room do it yourself - if it involves emptying the entire house it may be best to leave it to a pro if the house is full of stuff. I did everything myself aside from the staining - better half was an art major in college and is much better than me with a brush. **Protip do not use the stain and poly in one... ever - I am not complaining about the results but it was very sticky coming out of the can and that made it difficult to apply - it also did not give a shiny poly finish**
Here is my story - I rented a sander for this closet I was turning into a laundry room - it was at one point already a laundry room. I bought a used washer and dryer and was going to install it but the closet had nasty 80's carpet. I opened my trap to the better half and said "how about before I put the washer and dryer in I tile in there". So I pull up the carpet and pad, underneath I find stick on linoleum tile so I chisel that up and find painted hardwood - tile idea was scrapped and I spent a long weekend running to Home Depot to rent the sander and refinishing the floor. Here are some photos: