New to this myself - but...
The most important part is lighting - what lighting do you have?, how many watts are the bulbs? How many bulbs?
If they are standard lights then they will be very low light....despite looking bright!
Regarding layout its all personal - imagination is key but dont put all the short ones at the back and the tall ones at the front or you wont be able to see the contents of your tank. heheh.
Short plants at the front, medium mid way and tall plants towards the rear - then move them about (so not so uniform in layout) until you make a pleasing setup in your eyes.
Not hand any problem with plants against my heater, in fact I purposely hid my heater behind some as its ugly!
Have a search through the forum (or google low light aquarium plants) as lots of threads about plants more suitable to a low light tank.
I have a low light tank at the moment and have been quite sucessful with:
Java Fern
Ludwigia Repens
and a load more recommended to me in the LFS but I dont know the names (doh!)
Planst are all growing nicely (if a little slowly)
Java Moss is another carpeting plant that would be ok in a low light tank.
As I say have a quick read through any threads which sound similar to your question - far more helpful people out there than myself but this is a very common question!
BEWARE though - this CAN get pretty addictive!
