I've not played with the levels at all as I'm still working my way around reaper.
Fair enough, but try and tweak the levels quickly with each track you add to give you a rough mix. That helps you hear what's going on when you record the next track, makes it a lot more fun to play along with and saves a lot of time when it comes to the final "real" mixdown.
We all gotta start somewhere right?
Absolutely! My first recordings were on a Fostex X-15 cassette multitrack. Four tracks of hiss with a 15 minute record time:

Oh yeah - very easy to make a mistake and record over what you had already laid down.
How would you suggest I "tame" the low end. Just eq it out?
That's it! See? You're getting the hang of this already ? That's the basics of it, but if you want to fill your head with more of the tech stuff:
I'm not sure if Reaper has "low-cut" switches (which kill all of the frequencies below a certain point - usually somewhere about 40Hz). If it has, you should turn them on for any instrument that doesn't need really low frequencies (in other words, everything but the kick and bass) - that'll go a long way to clean up most mixes and prevent you wasting a lot of headroom on frequencies that are not needed.
Then use the low shelving EQ (often just one knob, labelled "Low" or "Bass"). If it's a more advanced Low EQ, it may have a second knob for "Frequency" or "cutoff point" (which sets the frequency at which the EQ starts working - a low shelf cuts from
that frequency down) in most cases, set this to somewhere between 75Hz and 125Hz (cymbals are just about the only things you'll set it higher for).