Nedd, welcome to RCU and welcome back to R/C flying. As Rog said, most people choose to begin with an ARF to start with. However, if you've got your heart set on building a kit, go for it. Sig makes great kits, I think it would be a great choice.

Here are my thoughts on radios. I have a Futaba 6EXA. For me it does everything I want, except for two things, not enough memory (only 6 planes [X(]) and I would like a timer with an alarm (nice to have, but not a necessity). A small number of people report that they outgrow the features of such a radio due to them wanting advanced mixing, more than 6 channels, etc. However, since something like 80% of the people will never require such stuff, I often suggest it for beginners who are willing to spend a bit more.

However, there are other choices. If you buy a basic 4 channel radio, such as the Futaba 4YF it's going to cost you a little more than $100. This radio will work just fine to begin with. Once you've learned to fly your trainer you will begin to have a better idea where you want to go with this hobby. If you think you'll mostly fly traditional 4 channel planes, but perhaps try out retracts, smoke, bomb drops, or a few other gadgets, then a 6 channel should do just fine. However, if you start drooling over quarter scale, 3D, and other planes that can demand more radio features, then you may want more than a 6 channel radio offers.

By starting out with the 4 channel radio you give yourself a bit of time hanging out at the field checking out other types of planes before you decide. When you do make a choice, you'll probably think "why did I waste my money on a 4 channel?" However, when you look at the money, it's not really wasted at all. The cost of a typical flight pack (receiver, battery, servos, switch harness, etc) is around $100. If you begin with a 6 channel computer radio you will need to buy a flight pack when you get your second plane. Buying the 4 channel means you bought the flight pack first and just happened to get a basic transmitter for free. When you upgrade to a more advanced radio you'll be able to use the flight pack with it, and you'll have a spare transmitter in case you need to send in the better radio for service.

And finally my thoughts on converting to a tail dragger. As Rog said, most trainers are trike gear for a reason, they offer easier ground handling. However, many people over the years have learned to fly with tail draggers (such as me). So, while it's possible to learn with a tail dragger, I agree that trike gear is the preferred setup. If you really want a tail dragger, there are kits out there that come as tail draggers. Here are a few examples:
Telemaster: http://www.hobby-lobby.com/tel40gas.htm
Senior Telemaster: http://www.hobby-lobby.com/srtele.htm (if you like big)
Sig Kadet LT-25 (going toward the small side)

And while it is possible to convert a trike kit to a tail dragger, you face the challenge of getting the gear in the right place, and slightly more difficult take offs. A compromise would be to choose a trike gear kit, and build it as a trike, but while you are building, install the pieces needed to move the main gear to the appropriate place to fly it as a tail dragger. Once you've learned to fly it as a trike, it would be a simple task to relocate the mains and add a tail wheel.