Since English descends from Proto-Germanic, which descends from PIE, would either of those two languages be relatively easy to learn (compared to, say, Japanese), or has the language changed too much to be learnable? Certainly people are able to learn Latin, especially those native speakers of Romance languages and English, so would they have much difficulty with Proto-Italic?
This is subjective, but take into consideration the following points.
PIE was a quite complicated language with multiple cases and rich inflections. It had more complicated morphology than English, but compared to Latin, German or Russian it does not look too exceptional.
Much of PIE vocabulary is quite well preserved in Latin and Greek so for a person familiar with modern European languages many roots and stems will be easily recognizable.