yes those tektros will fit.
and yes its complicated to make a switch....
dunno what your opinion of expensive is... but if 100 bucks sounds expensive than rather do not have thoughts of redesigning a complete bike .... the folks who are experts in modding their bikes know all too well that a budget of lets say 300 dlr just get you started...

the price difference between mariner and speed d 7 versus speed P 8 is in the letters...
D = deluxe
P = Premium
on the P bikes almost every part , from spokes to rims, to cranksets, to chainrings, chain, seatpost, saddle , handlebar, grips, brakes ...
is a small bit nicer than the deluxe counterpart .....

If you know the extra price increases of every part its a super bargain to go with the P bikes ....

thor