artisan

I suspect this is a fairly dumb question, but I'm just re-entering cycling after 20 yrs of being away (I'm fity-ish).
I have the subj bike that I'd like to convert to a more upright 'comfortable' bike but retaining some of the original benefits of original components and am wondering if its feasible or economical to do.

I'm thinking:
Slightly bigger tires (and wheels?)
Straight handlebars
Comfort seat

I don't have a lot of money to spend on a new bike and this one's in great shape, other than needing some tuning.

Does this make sense economically?