Visa can be purchased upon arrival in Kathmandu. Make sure you have a photograph and cash in USD handy.
Accomodation in KathmanduThere's a lot of hotels and guesthouses around Thamel. Go to Kathmandu GH by taxi. Do not stay there, it is too expensive. But it's in the center of Thamel. Start searching there. Ask for the price, check the room and go to the next one. In Tibet GH you get a nice room for 10 USD. Tibet Peace GH is a good place to meet people, is quiet and has a garden which is rare in Kathmandu.
FoodPumpernickel bakery is the place for breakfast in Kathmandu. Their croissants are superb. If you want to eat meat in Nepal, order a yak sizzler. Don't eat steaks. I got badly sick because of eating a garlic steak in Alice's.
Chicken is ok. Do not miss having a traditional Newari meal.
Plan at least 10 days for trekking. If you think you need guide and/or porter, go for it. They need the money and you can afford it. If you do not want to trek on your own, try to find a companion in the internet (Lonely Planets Thorntree) beforehand or do some activities (Chitwan, Rafting) before heading on the trek. You will always meet people en route or in the guesthouses. Try to avoid altitude sickness. Stick to the rules. Nobody is immune. Bring your own four seasons sleeping bag. The ones for rent are not warm enough and it gets extremely cold at night.
Following are the main trekking routes:A meal is 2 to 3 USD. Beer is 2 USD. Accomodation is 5 to 10 USD. On the trek beer and soft drinks are most expensive, followed by food and shower. Cheapest is the accomodation.
RaftingIf you are not afraid of water and feel fit enough, do it. Listen to the safety instructions, you might need to remember them when falling out of the raft. Kali Gandaki is a 3 days raft, not too difficult and not too easy.
NightlifeDon't go to Nepal for nightlife. Busy Bee Café in Pokhara and Sam's pub in Kathmandu are my favourites.
PashminaDon't buy these shawls, if you don't have to. Vendors might sell you anything for the price of a pashmina.
North FaceIf you want to buy quality trekking gear, do it at home. If you have to buy in Nepal, try a few shops. Check the quality. Make sure the zip is YKK. Don't buy North Face.
KathmanduDon't stay there too long. You're getting mad with the traffic in the alleys.
PokharaNice and warm. Reserve a day for the lake. Friendly atmosphere.
BhaktapurBrings you centuries back. Stay at least two nights.