My girlfriend has a res too. She is slowly getting around to letting me buy her all the stuff it needs.
Right now the most important thing to get will be the dock. If the turtle spends all of its time in the water its shell will eventually begin to rot. It will start with pinkish patches on the bottom of the shell. http://www.austinsturtlepage.com/Care/caresheet-red_ear_slider.htm
That page will give you all the basic information you will need to know. The people on the turtle forum are very helpful and can answer any other questions you have.
There are tons of ways to make a dock. A lot of people on the turtle forum like to make above tank basking areas. It gives the turtle more room out of the water and then you can fill the tank all the way up.
I bought my g/f one of these docks and her turtle really seems to like it. Zoomed turtle dock
Its really nothing more then a piece of hard foam on a rail so it can move up and down with the water.
Heres the link to my photobucket album with the turtle projects I was working on. The ten gallon was setup so that I could take care of my g/f's res for a few days. The 30 gallon was never finished as it wasn't coming out the way I wanted. There was supposed to be a waterfall on the left and basking are on the right. The little rock outcroppings were going to have pots with various plants growing in them and moss stuck here and there. This is now my planted tank.
Aquatic turtles must be in water to eat. Has something to do with the way they swallow. If you're worried about the food clouding the water you could feed him in a tupperware container with a few inches of water.
IMO a piece of plexi glass would probably be the easiest and cheapest thing to make the basking are out of. Cut it to the size of the top of the tank with a piece that extends out to use as the ramp. Boil the ramp piece to make it soft and then bend it down. Once it cools you can cover the plexi in whatever you want. Some people like to silicone gravel or sand over the entire thing so the turtle has something to grip on. After that all you need is a fence around it to keep the turtle from exploring outside of his tank.
I was just thinking that with the velcro it would make the basking area removable for easy cleaning of the tank.
Make sure to post of some pictures when you're done. I'm interested to see how this turns out.
It's been a LONG time!
Since then, she is in a 50 gal... I'll post updated pictures soon.
Right now I have 8 tanks set up, two RES, one box turtle, one fire bellied toad, some breeder tanks for goldfish and snails... etc.
What kind of lighting did you use? I would suggest a reptisun or equivalent with components of UV A and UV B. Try a piece of cork bark for a temporary raft. In a crunch, I've used the styrofoam lid of an old beer cooler as a stop gap. I would lose the gravel and add small stones. Turtles leave a lot of fertilizer that you will need to siphon off.
A temporary dock could be made using four clay flower pots and placing (hot glue) a piece of acrylic or plexiglass on top. Make this your basking spot by placing a heat bulb or ceramic heater over the spot and raise the temp to about 85-90.