It's best to stick with a DPS spec guardian anyway if you're planning to go through the PvE content solo, otherwise as a tank spec it'll take a billion years to kill things... I should know, I ran through the entire game from start to where I am now as a Tank specced Vanguard. Some of the content I did solo but most of it I ran with Jeff, Mav and Kus.
Solo tanking with a healing companion will ensure that you'll never die, but it also means that each fight will be very long and drawn out, especially boss battles.
Also, don't let us tell you what you should spend your skill points on. It's much better to figure out how everything works on your own and if you really need to respec, you can through a vendor on the Fleet station or on Coruscant. Just go with whatever looks right to you and you'll most likely come up with a spec that works for your play style.
Don't really need to worry about specifics until you reach end game and start doing hard mode flashpoints and ops and that kind of stuff if you choose to do that kind of jazz.