Does my MacBoo Pro use a SATA I,II,or III connection?
SATA I 1.5 Gb/s I don't recommend a SSD with your machine, it just doesn't have the faster SATA II or III.
Is the laptop a unibody?
The free MacTracker can give you more details.
Does the SSD need a special "tray" to fit in the laptop?
No. That's for those who can replace the Superdrive with a SSD, it needs a sled to fit.
I read good things about Samsung 830 and 840 250GB SSD... will it work?
I recomend a 7,200 RPM boot hard drive with your slower SATA I, it gives more space, a lower cost and it's more in line with your hardware and easier to install than messing with a SSD and TRIM etc., with OS X 10.6 which you will have to install.
A hard drive with OS X 10.6 you just install it, no tweaking necessary. You can't upgrade to OS X 10.7 or 10.8 on that machine.
Can i do the upgrade myself with out being a certified computer repairman?
Yes, but you have to consider this, the machine is over 7 years old and considered "Vintage" and certainly outlived it's normal 3-5 years of a typical laptop.
So you got it for free or cheap, but it's a very old machine.
In my opinion it's best to leave it just as is and milk it until it dies.
However it's possible to max the RAM to 2GB
2 - 200-pin PC2-5300 (667MHz) DDR2 SO-DIMM
Install a new 7,200 RPM hard drive
And erase and install 10.6
Software Update to 10.6.8 and live with it until it dies, as you can do nothing else.
It's a waste to spend any large amount of money on that machine, especially a SSD when the machine can't handle it (also complicated to install on older machines with 10.6) nor can use a later OS X version
OS x 10.6 is still receiving security updates, but Apple is not changing the version number, we are stuck at 10.6.8
If you don't have 10.6, (Apple Menu > About this Mac) you can buy the 10.6 white retail disk online at Apple Store.
There is some free software that still works with 10.6
LibreOffice, GIMP, Firefox and a free version of CS2
Also 3D games, Cube 2 Sauerbraten and Nexius Classic
If you want to spend money on a Mac, get a new one. Then buy all the software you want because it will last 3-5 years depending upon use.