How to apply China tourist visa for a Nepal tour operator?

Dear Sir/Madam,

I am a travel agency business holder from Kathmandu. We organize Beijing- Lhasa- Kathjamndu, Xininig- Lhasa- kathmandu, Chnegdu- Lhasa- Kathamndu tour for our foreign tourist from the world. This time I am going to meet group of tourist who travel from Beijing to Lhasa by Train and overland tour from Lhasa to Border. I haven't been Lhasa and beijing before. so would like to visit this places and also would like to travel with our tourists from Germany there in sept. I would like to welcome them in Beijing Airport myself with driver and local guide of beijing. I am also going to visit Chengdu, Shanghai in advance than group arrive in Beijing. How I can apply Chinese visa here? As I am own from Nepalese travel agent, also I can book myself hotel in Beijing or chengdu, flight to Beijing or chengdu, also I can show full bank statements, tax paper, company documents, hotel booking, flight booking myself. Stil I need to have Invitation letter from China? if yes, my Local agent in Lhasa can write me Invitatation letter and that is OK for Visa apply? as far I know people who travel from Kathamndu to Tibet get only group visa for china. since I travel beijing first and then to Lhasa, Can I get Visa in Passport or same group paper visa? what is normal chinese visa fee?