Can I get baptized into the LDS church and attend the temple if I get a tattoo?
If you have a tattoo, you can definitely learn the gospel and be baptized. Then you can prepare to go to the temple and attend the temple and do everything a normal LDS church member can. As a lifelong Mormon, I don't really judge people by their tattoos, I have Mormon friends with tattoos, I see people walking through LDS temples with tattoos occasionally, and overall it's not a big deal to me.
If you already are a baptized member, and you just got a tattoo, you haven't necessarily committed a sin. But you might not appreciate fully the viewpoint of the LDS church (or God, perhaps?) on tattoos. First, tattoos are not super evil or something like that. But God teaches us that our bodies are sacred, and they should be treated like holy temples. The treatment of the LDS temples is similar to the way we should treat our God-given bodies.
I think there's definitely a loosely-defined intuitive element to the tattoo discussion, and you could certainly argue that tattoos actually look pretty cool! You could argue the point all day. So this may take some personal prayer and pondering / meditation to figure out. Everyone has to think this stuff out for themselves, in the end. And if you decide you love tattoos, you think they're great, and so on, it's then your burden to figure out why your beliefs differ from the LDS Church and what you're going to do about it. Quit the church and become a tattoo-loving person? I dunno--that seems like a really uneven exchange to me. But it's your life.
In its teachings on tattooing, the LDS Church again emphasizes that our bodies are temples (1 Corinthians 3:16-17). If we defile our own bodies with tattoos, that probably means that we don't understand temples, their significance, and their purpose (a topic worth studying). So it seems unlikely that a member of the Church who just went out and got a tattoo would be given a recommend to enter an LDS temple.