The plane will work great. it comes with the fuel tank, just assemble it according to the instructions.

In addition to the engine you will need some fuel line, some spare glow plugs and a glow igniter. An electric starter is nice but not absolutely necessary.

You can likely find all of this at a good local hobby shop, but here are some links to give you an idea:

http://www3.towerhobbies.com/cgi-bin...?&I=LXFRM1&P=0

http://www3.towerhobbies.com/cgi-bin...?&I=LXD697&P=7

http://www3.towerhobbies.com/cgi-bin...&I=LXL396&P=ML

The glow plugs and prop(s) you select will depend upon the engine.

One of the best engines on the market for a 40 size airplane is this one: http://www3.towerhobbies.com/cgi-bin...&I=LXFMD5&P=ML

Tuning is no big deal if you have any other automotive or small engine experience. Even if you don't, just follow the instructions.

Another good idea is to find someone at the local flying club to help out. Ignore the know-it-all's who are always tinkering with their engines and have all sorts of excuses why they don't run right. Instead, hook up with the guy who never seems to touch his and just flys. He will steer you in the right direction.