The company WAC has a lot of outdoor lighting options. I'd recommend visiting a lighting store for a consultation with your layout. We use solar-powered lights that are faint but don't require new wiring, just rechargeable batteries in each unit. That might be your easiest option, but it won't light up the whole tree by any means.

One watt per foot of tree is the old standard, what you want is angle cut collar on a med. to narrow beam spread, composite or brass to avoid rot. You do not want a flood because as the tree grows the light needs reach the top, so a more focused light is required to drive the light up.

http://www.focusindustries.com/

you can call their customer service and they can help you, they make a great product with a great warranty and they know the biz very well. I almost always used them. WAC is good but Focus is really a landscape lighting company. Tell them what type of tree it is as well.

Also, as a side note, IdK what your electrical plan looks like but running wire 400 feet tends to loos rigidity so you may also want to talk to them about the transformer options.