I'm playing through BG1 for the first time, and I'm not doing a great job of keeping my companions alive. Xsar (?) died at the entrance the the Friendly Arm, and now Garret(?) the bard just died in Beregost.

I can't really be bothered to keep reloading old save games every time a companion dies, so is it a big issue? there seem to be a lot of companions, and I know that Minsc/Boo is supposed to be a classic... so i'd need space for him anyway.

He did have a funny monty-python song about running away though.... but his running away seemed to involve going in a big loop and then coming back to stand next to the assassin, who then killed him... so he kind of deserved it.

It's not strictly necessary to keep any of them alive, though you have to remember that you are directly responsible for their deaths. Also, there's a finite number of NPCs, so if you kill off all the Good ones and your reputation is 19+, the Evil and Neutral ones will be really pissy.

I find Minsc, Dynaheir, Jaheira, Khalid, Imoen, Branwen, Ajantis, Kivan, Coran, Xan and Yeslick to be bro-tier, though, and I'll reload if any of them dies. Other folks I generally have only in the party for a short time to fill the gaps, or to finish their individual quest and then boot out forever.

Xsar and Garrick are hardly great losses, so just replace them.
If using the BG1 NPC Project mod, though, Xsar is one of the best (as in having more content added) characters, and he and Monty are great fun to have in your party.

You can solo the game so don't worry too much about companions.

Garrick was great for his pick-pocketing skill. With a few reloads in a few choice locations, you can find items that make the game a piece of cake. But you'll still be fine without him.

its his first time playing so I kinda doubt he can solo it,,

Some players even have an easier time soloing on their first attempt.

You do realize that you can resurrect fallen compansions at any temple, right?

As long as they are still in your party and it costs 1000? gold.