I cannot think of any period better served by 1/72 scale than WWI. ‘Plastic Soldier Review’ will be a great help in finding figures. ESCI and AIRFIX both make Allied tanks. In reality, most German tanks were captured Allied tanks, too. But if you want to use A7Vs or armoured cars (or French tanks) you may have to rely on paper models. Look up Landships II for a good selection of these.
In theory, painting should be pretty simple. Personally, I wouldn’t think a painting service would be worth the trouble… but I’m a cheapskate with the time and inclination to paint.
I’ve been on the verge of doing WWI Mesopotamia (or A-H vs. Italy) for a couple of years now. Please post your experiences! Even if I don’t take the plunge I can live vicariously!
Self taught, persistently behind the times, never up to date. AKA ~ jeff
More verbosity: http://petiteguerre.blogspot.com/