I noticed that no one yet has mentioned undelayment. This is an extremely important material with any tile job.
The smaller the job, the more you may be able to do without it, but honestly, every tile job should start with Hardibacker/underlayment. Also, if the tile is over a crawlspace you need supports depending on the weight of the tile. There are lots of things to consider when deciding to do this yourself.
Secondly, it is very important to pick out a sturdy tile. There are really cheap tiles for sale that will last barely a few years.
I would absolutely not do it yourself IMHO. The work, preparation, materials and expertise are worth what the tile layers charge you.
Believe me, it is VERY hard work, and if you want it to look professional, you really should hire a professional.
A professional tile setter usually charges around 2X the cost of the tile or more. Yes, it is a high price, but you cannot put a price on knowledge and experience (not to mention it is very hard work...did I say that before

)
Good luck whatever you decide!