Cool! Now, it’s time to contact the vocations department there, and start discerning with them whether you’re called to priesthood in that diocese!
Or does diocescan Priesthood have its own special spirituality that is exclusive to diocescan Priesthood?
I think that it would be helpful to make a certain distinction, here. I don’t know if there are proper ways of describing it, but the distinction that I’d like to offer is between the charism of the diocesan priest and the way that a diocesan priest lives out his spiritual life.
The charism of a diocesan priest includes sharing in the ministry of his diocesan bishop, to whom he’s promised obedience. It includes shepherding a particular part of his bishop’s flock, and caring for their spiritual and pastoral needs. These days, it means never becoming a permanent part of a parish community, but rather, being willing and able to move to a new community at your bishop’s request, after 6 or 12 years, or less! It means always being “on”, always being in the spotlight, always being at your flock’s beck and call. These days, it usually means being there for your people, but always going home to an empty rectory, and being able to handle living alone, without the kind of 24/7 support that religious communities embody. (It also means being taking responsibility for reaching out to your brother priests in the diocese, building relationships with them even when it’s inconvenient.)
Contrast that with the way a diocesan priest lives out his spiritual life, which is what I believe that you’re talking about. A word of caution here: I don’t know for sure, but it certainly seems to me that any organization that you join prior to entering seminary (Opus Dei, any Third Order community) will be something that the admissions committee takes into consideration when they make their admissions decisions. On the other hand, any organization that you join after entering seminary (and especially, after ordination) would be subject to obtaining the permission of your rector or bishop. (I’m not saying this with 100% certainty – but it sure seems like this is the case.) Just a word to the wise…