It is very simple to get visa of Nepal. After reaching at Kathmandu TIA airport you can get visa which will just takes 20 minute to proceeds. You also need some cash to be prepared. 15 days visa charge: 25 USD (per person) 30 days visa charge: 35 USD (Per person) 90 days visa charge: 100 USD (Per person)

There are many people who are guiding in the Himalayan area but you should choose a guide who have government certified license and speaks good English language. You can search in Google freelance guide in Nepal than you can see piles of Web pages than see who have good review than choose him and pay 30 USD a day and 20 USD a day for porter. They will deal with their food, accommodation and salary with this money a day.

Kathmandu and Pokhara are the main gateway of all trekking in Nepal where you can rent sleeping bags, pant, shoes, down jackets normally. You have to leave some money there when you hire those gears just to be save they will ask with you some deposit.

It is very simple to get taxi in Nepal, you just show your hand than they will stop easily and then you can deal with them regarding where to go and how much does it takes.

Yes as Nepal has many types of trekking route you can trek for sure. You just need to talk to your friend who have visited Nepal recently or ask with Nepali agent or guide they will let you know. Everest Base Camp, Annapurna Base Camp, Annapurna Sunrise trek, Poon hill trek etc are easiest trekking trails but it is better to go with local guide who knows everything and can pretends the events such as natural disaster, danger area, forest area etc.

It depends on where are you trekking and which season will you be choosing to trek to determine the accommodation difficulty. Nepal between September and December or March to May it is difficult to get accommodation but if you have guide or porter with you they will call and reserve before you reach to the tea house. Otherwise in general you can get easily accommodation on cost 5 USD a night in a tea house based accommodation.