I've received an orchid bought from the store, I forgot the type of
orchid but it is the one with the large round leaves, thin stems, and
white/purple flowers. The pot was poor and doesn't have any holes in
the bottom. The result is that the bark seem to look permanently
moist and I can see some tiny bugs crawling along it.

The couple of leaves have got burnt and fell off (I think I put it too
close to the window).. Only have a tiny leaf now below. I think the
roots might be rotting from the improper water venting.

I'd like to know the proper way to re-pot the plant, with some new
bark (what kind?) and the pot with be modified with some holes drilled
on the bottom.

BTW I also have another orchid, a different type, it's doing really
well, over 2 ft high, but the roots are sticking out the pot further
and further. What do I need to do to ensure it's survival? It has 3
stems in a pot.

Sorry about the lack of details I'm really new to these plants.